First off
THIS IS A GAME
We were all new once. Some people don't quite get that. So they think they can get away with being total jerks to new/low level players. Sure even I will leave low level lobbies but I am currently V-100, I just feel out of place with 3 people under level 50.

Alot of the newer heists give ALOT of xp and money. Don't be suprised to find someone with less hours than you having a much higher level. Remember: playtime > level. Most people will refer to you as new when you have less than 100 hours played.

Even I get kicked from certain lobbies or I will leave them. Don't be afraid to leave a room that is not fun or a good fit for you. Also some people were raised on CoD so they'll just abuse the kick button or abuse you, lobbies like that don't need you and you don't need them. There are alot of very nice people on CrimeNET but children of CoD wreck the game for most of us.

So read on and I will teach you some tips and tricks for getting better at this wonderful game.

Good Lobbies vs Bad Lobbies
Knowing this is the key to enjoying this game. There should be a few things you should be checking before just jumping into a game.

The Host
They can be the nicest person ever or the biggest self-entitled jerk ever.
It's kind of trial and error but a good host means a good lobby.
But it kind of annoys me that you can't see the host's level from the CrimeNet screen tho...

The Heist
"Hey look a group doing a OVERKILL Rats, I'll just join them for easy xp" <- Don't do that.
You'll either get kicked or fail horribly (and then get kicked). Under level 50 you should be looking for normal, hard or very hard (if you're feeling lucky) and for heists try Mallcrasher, Four Stores, Nightclub, Bank Heist or a low difficulty Firestarter.

Making your own lobby.
It doesn't hurt to make your own lobby, expecialy when you just want to focus on one thing,
ie. xp/money/stealth practice.

• Listen to your crew, they can really help you pick the best heists.
  
• Don't just pick a difficult heist and hope high level players join, you'll learn nothing getting carried. Plus most high level players won't stick around to babysit.
  
• Pick heists you are fairly sure you and your crew can pull off, it doesn't hurt to try new/different heists.
  
• Don't be scared of the kick button, people will troll. There's a very long list that I won't go into here but you'll know fairly quickly so kick them before they have a chance to run off and rejoin later.
  
• Don't listen to cheaters/hackers (I'm not talking about Hoxhud users). All the fun is removed when someone can just press a button to win. Cheaters will join and will either be unskilled/try to make you join their lobbies or just mess around, it's best to just kick them.
  
• Don't forget assets. Sure it's not just up to the host to buy them but if there's one or more you think that you'll need buy it.
  
• Have fun and happy heisting. Like I said, "this is a game". If you're not having fun, why play?

Vote or Host kick?
Most people will just have it set to host, but you will get the odd vote kick lobby. Personally me and my friends will just leave it on host kick.

Cheater Auto-kick/Cheating hosts
Annoyingly Overkill didn't block cheaters from making lobbies, so they basically bypass the auto-kick. I've said it before, you won't learn anything from being carried or cheating. If you find a cheater, ignore them and just go on.

The first question you should ask yourself is:
What role do I want to play?
Currently I'm a Techforcer, since someone has to help those Inspire guys open doors.
Here's a list of skills that will help you and your crew. All are low tier because this isn't about builds, just skills that are usefull for anyone to have.

Mastermind:
Cable Guy 1 point for basic, 3 points to Ace
Aced this skill gives you 6 cable ties.
Allowing you to take more hostages, meaning in a stealth run you don't have to shoot as many civis.

Endurance 1 point for basic, 3 points to Ace
Basic: Increases your stamina by 100%.
Aced: Increases stamina for you and your crew by 50%.
This is a great low-tier skill. It works great with Sprinter from the Ghost tree.

Cable Guy 1 point for basic, 3 points to Ace
Basic: You tie civis 50% faster
Aced: Increases your supply of cable ties from 2 to 6.

Control Freak (Tier 2) 1 point for basic, 3 points to Ace
Basic: Civis remain intimidated 50% longer, noise created intimidates civis.
Aced: Unlocks the Inside Man assets.

Enforcer:
Transporter 1 point for basic, 3 points to Ace
Everyone should ace this.
Aced you move 50% faster carrying bags and throw them 50% further.
This skill is never not usefull, as you'll always be moving bags.

Technician
Nerves of Steel 1 point for basic, 3 points to Ace
Basic: You take 50% less damage when interacting with things, reviving teammates included.
Aced: You can use steel sight while in bleedout.

Drilling (this is kinda part of a build but I might as well talk about it here because it's very very usefull to know.)
Hardware Expert (tier 2) 1 point for basic, 3 points to Ace
Drill Sergeant (tier 3) 1 point for basic, 3 points to Ace
Silent Drilling (tier 4) 4 point for basic, 8 points to Ace
Total: 20 points (not including the extras to get to the tiers)
What it gives:

• You fix drills 25% faster
  
• Gives the drill a 30% chance of auto-restarting when it jams
  
• Increases the drill speed by 30%
  
• A silent drill, meaning guards/civis have to see the drill to notice it (they'll still head towards it if it jams, only getting sus if they see it)

You can live without silent drills for a normal loud tech build but it is a must for stealth builds.

Ghost:

Sprinter 1 point for basic, 3 points to Ace
Basic: The time before stamina regeneration starts is reduced by 25% and the regeneration of stamina is increased by 25%.
Aced: Your sprint speed is increased by 25% and you have a 25% better chance dodging enemy fire while sprinting.

Cat Burgler 1 point for basic, 3 points to Ace
Basic: You take 75% less damage from falling.
Aced: Damage from not fatal falls is turned into armour damage, in addition your custody time is reduced by 50% (only on normal and hard as very hard and higher there's no timer)
Remember: armour damage > health damage.

Fast Hands (tier 2) 1 point for basic, 3 points to Ace
Aced this skill lets you pack and interact with loot bags 75% faster.
It's a skill that will make you life alot easier.

Cleaner (tier 2) 1 point for basic, 3 points to Ace
Basic: You deal 5% extra damage to special units, you can now buy the Body Bags asset. Which contains 3 extra body bags that your crew can share.
Aced: 1 Aditional body bag is added to your inventory, for a total of 2. (All players defaultly have a single space for a body bag, aced this skill increases it to 2 allowing you to carry 2 at a time. With the asset, you provide 5 body bags.)

Shinobi (tier 3) 1 point for basic, 3 points to Ace
Basic: Your walk speed is increased by 25% and your crouch speed is increased by 10%.
Aced: Enermies make 95% less noise when shot or meleed to death. (By you only)
This skill is vital for stealth as without it other guards will hear you and they'll just sound the alarm or press a panic button. I've done so many stealth runs where I ask, "do you have shinobi?" only to hear "what's shinobi?". Shinobi is vital for stealth since for some reason guards react more to the sound of another guard dieing on the roof than the sound of someone yelling "get down on the ground" very loudly. Sure it is tier 3 but atleast one of your crew should be a high enough level to have it by the time you want to try to stealth.
Note: Aced Hidden Blade is the same as Aced Shinobi, but the basic is different.

Fugitive

Hidden Blade (tier 1) 1 point for basic, 3 points to Ace
Basic: Increases the concelment of your melee weapon by 2
Aced: Same as Shinobi (see above)
Personally I go for Shinobi for the movement speed but if you want a tier 1 version or going fugitive build, this isn't bad.

Thick Skin (tier 1) 1 point for basic, 3 points to Ace
Basic: You stedyness is increased by 10
Aced: Increase the armour of all balistic vests by 20
The steadyness is nice but the main point of the skill is the aced version. It's what mades a good Crook dodge build.

Perk Decks
I ****ing love perk decks, they're a good replacement for the old tier perks. You should really max them all but I think either Armourer or Rouge are good ones to start with so you can survive while you get enough xp for the rest.

Loadout Slots
Slot 1: Unlocked by default
Slot 2/3: Offshore cost (I can't recall how much, but it's alot)
Slot 4: Level 100 + Offshore cost
Slot 5: Level 100 + Offshore cost + Tabula Rasa Achivement. I have a guide on the subject http://gtm.you1.cn/sharedfiles/filedetails/?id=359248748
Why am I talking about this? Because it's useful to know and to have multiple builds set-up.
Sorry about not including how much each costs but I can't find the numbers anywhere and I payed mine off a long time ago.
Still it's not hard to get enough money to atleast get slot 2 unlocked, then you can have one loud/ one stealth or one armour/one dodge builds.
There are plenty of guides on the subject of builds so that's a good place to start.

There are alot of tiny little things you learn while you play, here's just a few:

• Single player doesn't hurt. Scout the map, learn where cops spawn and so much more. Sure the bots won't help you move bags but they can man-mode cops.
  
• Learn what maps are loud only. It annoys alot of hosts to be asked "Loud or Stealth?" at the start of every heist.
  
• Don't put Medic and Ammo bags out in the open, put them in cover and far enough away from each other so it's easy and safe to use them.
  
• You can be knocked down 3 times (4 with the Nine Lives skill from the Ghost tree) keep count and know when you use a Medic bag, as it restores your number of knockdowns to zero. Pick the right time and don't hog them (don't hog ammo bags or body bags either).
  
• Cloakers may seem OP but they're not. A few good shots to the head and they're dead. But always kill cloakers BEFORE getting team-mates up, they'll kick you down too.
  
• A Bulldozer's head is it's weakpoint, focus your fire there.
  
• Shields are weak to attacks from the sides and behind, positioning your team is key to taking them down. They're just as strong as any other green SWAT.
  
• It doesn't hurt to retry, unless it's a pro-job.
  
• The best way to learn stealth is to watch someone else do it, hop on cameras and watch (as well as marking guards)
  
• During stealth, even if you're just watching, don't wear any armour. Street civis and protrolling guards may see you.
  
• Also during stealth, ask if it is safe before dropping in.
  
• Don't get greedy, sometimes people don't want to pick every depost box.
  
• If you are short on friends to play with, check out the Crews and Clans section on the forums.
  
• Last of all, Have Fun. Like I've said many times, this is a game to be played for fun. Don't let anyone tell you any different.

First-aid kits vs Medic bags:
First-Aid kits (or faids) were introduced with the Fugitive Tree. They don't replace medic bags but they do restore max health. Basically you use them "like noobs use medic bags". Faids restore your heath but don't restore downs but you can carry a max of 14 of them and deploy/use them fast. The main advanage of faids is speed, they can be used fast and you can use them while running, unlike medic bags that you have to place in cover. Both have their place, so don't rule out bringing either. Just remember if you're going to spec for faids, spec for the full 14.

It kinda bugs me that the characters say "I need a medic bag" when they're low on hp, it leads to alot of confusion on when the best time to use a medic bag is.

Note: My thoughts on Hoxhud.
I'm not a mod person, but I know alot of people who love using Hoxhud. There's nothing wrong with it and it's not hacking but I'm just not a fan. If you want to use Hoxhud go for it. It has lots of usefull information and Overkill approves of the use of Hoxhud. It's still in beta and can't be used on XP and it's use at your own risk.

Other Note: My thought on PocoHud
Copy most of what I think about Hoxhud here with one exception:
"I ♥♥♥♥♥♥♥ hate Pocohud." You can put that quote anywhere you want, it's how I feel about it.
I should clarify a little I ♥♥♥♥♥♥♥ hate when people use it with all the notifications turned on as it'll spam the chat like there's no tomorrow. Basically Pocohud is Hoxhud with less bells and whistles and a feature to send a chat message when certain "events" happen. "Events" can basically cover everything short of each individual step each player takes.
This is what most annoying Pocohud players do, they set it so EVERYTHING is spamming the chat like there's no tomorrow and it's annoying as hell. Yes you can set it to only display for you but alot of people don't, hense why I hate it so much.