This guide is just a short collection of experiences and resulting best practices from my play through with the EA release to the day 180 (official end of content).

- Your base(es) can be attacked. Aliens come in through the hangers. According to description one type of Alien can appear everywhere, didn't have that happen since that type never attacked me.
You are limited to 15 soldiers or sentry guns / MARS in defense. :( But on the other hand, that's also about the maximum number of attackers.

- Be aware of build times and plan ahead. You will need more than 1 lab / workshop.

- Repairing airplanes takes ages. Try to not lose them. You might need to let some UFOs do whatever they do since you don't have a chance of shooting them down.

- The 3 rings you see when placing a base are the radar range for 1, 2, 3 radars.

- As every veteran of X-Com etc. knows, the best base is in Africa, near the birth place of humanity, where you can cover (with 3 radars) Europe too and a part of Asia.

The defense of Earth requires 3 things: money, money, and more money...

- Sell stuff you don't need. Corpses (keep one each to show visitors) are dead weight. Alien weapons cannot be used by your soldiers (but research them before selling all!). Alenium and Alien Alloys don't use space and at least at the "easy" level you will have more than you need. Still it's hard to say how much to sell.

- researchers and engineers that are not busy produce more money than they cost. A tiny bit only at start, but room upgrades make it better (bug?). Not worth hoarding them though, at least until you have the whole landmass covered with radar and interceptors.

- Your first base should grow to having 2 training places and 24 soldiers (or even more). You will often lose some of these guys if you don't "abuse" saves, and more often you will have wounded.

- Never recruit soldiers that are worse than 50 on average. Never recruit a soldier with red trait. Really good ones have above 60 average with no trait under 50. The available soldiers frequently change. At the start of the game have a regular look as recruits and select the best.

- Weapons are fairly balanced, every has pro and cons. That said grenade launchers are the worst and sniper rifles the best at the moment. Everything a grenade launcher can do, a thrown grenade can do better (until you have crack troops). Snipers can hit a fly in cover over half the map. Give them a nice roof to work from, if you can find one. (ladders can be climbed)

- Always have at least 2 shield carriers. Those things stop 2 shots on average from the front half. Use your shield carriers to scout and open UFO doors. Always have them carry one or more stun grenade. (Bug: Stun works through roofs)

- The first armor you research - ignore the "make sure you have enough" text and produce one for each soldier on the field. It's lightweight and relativly good defense. Those 20 armor make a huge difference!

- Lasers are cool! You will need (minimum) 1 reserve magazine for for rifles and 2 for other weapons, but aside from lower shot amount, they are better. Research later will make them even more awesome! It will take a long time until you have better stuff, so produce enough of them.

- The healing kit is important! Don't forget to have some on your mission. Bleeding wounds are a real emergency. You may want to change your sniper's pistol to a healing kit, if a sniper hits an Alien with his pistol, you have done something wrong anyway.

- Don't overestimate cover, especially half cover! The calculations work in a way that even in half cover there might be more then 100% hit chance. That does not mean though you should ignore it. ALWAYS use cover for your soldiers that aren't in 100% clean area. Hug walls and trees, they are your friend. Crouch can help. btw. Cars can explode, trains not (but "disappear" when hit.) Well, there is your problem. Trains good, cars bad.

- Never, ever, walk alone. I use troops of 3 to clear. The map is always 2x3 or 3x3 "areas" big. So one troop goes front, one to left, one to right. Better wait for other troops than go alone, to prevent flanking fire.

- Smoke reduces hit chance by 10% per field. It might help cover your backside. But you should not get into that big trouble if you adhere to the point above. btw. Smoke stuns a little. If you see an alien with 4hp or less, throw a smoke if you don't have stun. That even works before you hit them.

- Always reserve TU for reaction shots.

- Before you breach into an UFO, collect all your troops. Shields first, then machine guns and pump action heros. Do not storm ahead. The last room always has an alien, most likely the brain thingy, if that survived the crash. Always reserve TUs for reaction shots if possible, slow wins the day, go room for room.

- Civilians are deadly stupid atm. Ignore them on your turn, but look where they die, get shoot at or shoot themselves between your turns.

- There will be missions with timers. I hate them. Timers suck. Figure out for yourself why. (The devs have already said they will (optionally) make timers easier and they have already reduced reinforcements.)