1. Don't Be Afraid to Lose Guys
Everyone knows that death is an inevitability in X-Com; soldiers die often, and in large numbers. The intense feeling of dread this causes can be discouraging to new players. However, it's important to remember that your soldiers are all expendable. The whimpering rookie who's barely strong enough to hold a gun? Expendable. The cigar-chomping commander carrying Fort Knox in his backpack? Also expendable. As long as you have money to bankroll new recruits, no loss of manpower is going to cripple your game. I've played campaigns wherein I lost four or five whole planes' worth of soldiers (the plane included), and kept on trucking. Don't let it discourage you.

2. Sell Alien Loot
Nobody tells you this, but the paycheck you get from the UN council every month is worth almost nothing. Want to make some real money? Sell the priceless alien goodies you're raking in every mission! Every single gun you can pry from an alien's cold, dead hands will net you tens, or maybe hundreds of thousands of dollars (the cold, dead hands themselves are also worth some coin). Pace yourself when selling the rarer parts (like UFO components), and always keep at least one copy for yourself, but otherwise, have a bake sale. Go nuts. You'll be amazed at how much more lucrative it is than waiting for Brazil to up your allowance.

3. Don't Do Night Missions
This rule is very simple, and will dovetail nicely with number four; don't do night missions. The aliens have night-vision, and you don't. Combat is hard enough in broad daylight, but when your soldiers can't see four squares ahead of them, it's like watching chickens run around with their heads cut off. The aliens will rain plasma on you from across the map while Yakety Sax plays ponderously in the distance. Just say no; if you're raiding a crash site, wait until morning. If it's a time-sensitive terror mission, maybe don't do it at all. Which leads to the next rule:

4. If It's Too Dicey, Skip It
In the same way that excessive soldier death can be discouraging, it's easy for a new player to feel extreme trepidation if they don't do every single mission. Always remember that X-Com is about the bigger picture, and every mission is optional. So long as you're earning reasonably more points than you're losing, you can stay afloat month to month. If you lose points by skipping a mission (or screwing one up), so what? Earn them back on a mission that's more favorable, when it's broad daylight and you're better prepared. If you think one mission is a wash and will just sink your score, skip it and know that the points you're losing are nothing compared to what you'd have lost if you flew in and made a total ass of yourself. I once went an entire campaign without ever playing a terror mission, because I could mitigate the penalty by doing really well in other missions where the odds were better. The UN only cares that you're doing more good than bad, even if you have to call in sick a couple times when Brazil needs your help.

The same goes for air battles; you'll lose points for every UFO that gets away, but sometimes it's better to let them pass. If you throw all your little fighters against a big-ass battleship, and they die horribly, you'll have no craft left to fight the easy-pickins' who will come later. As long as you can earn enough points to offset the ones you're losing, you don't have to take down every craft.

1. Smoke The Ramp
This one is simple, but unimaginably important. The exit ramp on your troop transport is a meatgrinder; the aliens know you're there, and there's no cover -- it's a march to instant death. The way you can mitigate this is to smoke the exit ramp as your very first action in every mission. Before anyone in the plane even moves one boot, make sure one of them throws a smoke grenade onto the base of the ramp (set the timer to zero). End your turn so that the smoke will build--then, and only then, should you attempt to move your squad off the plane.

2. The Spotter/Sniper Method
A safer way to find and deal with aliens is to put your guys in a sniping position with good line of sight to the rest of the map (huddled 'round the plane often works), then make one unlucky soldier walk out and act as a spotter. If he sees something, deselect the spotter immediately and let his far-away squadmates open fire on the target. If they can't score a hit, your spotter may still have some time left to shoot or run for cover. With this tactic, you can have multiple soldiers fire on a target, while only putting one guy in danger. For added safety, you can hide your camping squad with a smoke grenade; they can see targets spotted outside of the smoke (all your soldiers share line of sight), but the aliens can't see in.

As you may guess, spotting is a dangerous job, so it's good to keep a steady supply of rookies on hand. If a spotter gets mauled, send out someone else to resume his position, or, if you feel you're taking too many losses, get back in the plane and leave.

3. Demolish All Farmhouses
Aliens, especially in the OpenXcom[openxcom.org] port (which I would strongly recommend using), love to hide in buildings. The farm tileset is where this tendency will be at its strongest, so it's a good idea to expell World War III-sized payloads at any and all hiding places before the buggers can get the drop on you. Remember: wood is brittle and vulnerable to all ordnance, but brick walls take the heavier stuff, such as explosive packs and alien weaponry.

4. Spam
There are automatic shots, snap shots, and aimed shots. It took me many failed missions to realize that aimed shots are a complete scam. Everything in X-Com is subject to lots of under-the-hood randomization, and even an 80% chance never turns out as good as it sounds, so never put all your eggs in one basket. If it's a choice between 1-2 aimed shots or a whole bevvy of snapshots, pick the snapshots every time. By the same token, always, always go with automatic fire in close-quarters situations, like UFO breaches. Typically, the more shots you can fire before the target can react, the better.