- If you are in a Hunt you can weld the doors of a room you're in and cancel the hunt, even if you don't rest. It applies to even non-"safe room" areas, but it doesn't work if enemies are already moving towards you.
- Taking out roaming xenos is a big part of stealth later in the game and it's easiest to do this with either mines or the sniper's silenced special shot. For mines you can use the hacker's drone or an auto sensor to lure enemies into them. You get a lot of command points to spend, and they regenerate, so don't be afraid to use them.
- If you are going to spend any time in an area then slapping down some sentry guns takes seconds. Just don't forget to pick them back up again.
- Save your purchasable skill slots for after you get a class specicialization because you will end up being able to buy some good class-only upgrades.
- You unlock the ability to passively train rookies later on, as well as a way to get rid of stress based debuffs, so don't worry too much about save scumming if you get in trouble or grinding out xp on green recruits.
- The Armored troop carrier does not trigger hunts and also rips enemies to shreds so don't be afraid to lure baddies into it. You can even use the map to drive the vehicle up and down roads to clear them out. It's fairly broken in some maps.
- Maps are persistent so doors that are welded, motion trackers dropped, or sentries deployed stay there when you come back with the only caveat is sentries will be broken when you come back.
- This also includes resources so it is a good idea to not strip search the place for everything on an early playthrough and to leave ammo, meds, or tools that are easily grabbed for later.
- This is ESPECIALLY true for ammo since marines only bring in 1 extra ammo each into a mission unless you buy a perk for them. While you can purchase meds, tools, and sentries with materials ammo can't be purchased. Don't be like me where you leave the first time on the first map with 16 extra ammo and leaving none for later. For an idea on ammo usage assume every marine will need a reload after a Massive Assault or whatever its called gets triggered. (I've reached a point early in the game where I'm getting attacked a bunch but I just don't have enough ammo and I think I need to restart.)
- I haven't played much but the Mineshaft is the first hard part of the game. Make sure by that point you have a way to kill aliens without setting off a hunt and have enough ammo for at least 2 if not 3 reloads when the game warms you something is about to go down.
- Don't underestimate walking when under attack. Your marines will still shoot and even though it isn't much any distance between you and the aliens is good.
- If no aliens are on the tracker don't be afraid to run. The longer you spend on a map the more aliens will spawn and the harder things become so try not to waste time.