Let's start on the base management side. The first thing you will want to do as you start the game will be to focus on getting satellite coverage over all countries as soon as possible. This is incredibly important as it serves to keep your council countries happy. When playing on Iron Man Classic, it is very likely you will loose at least one country at the start of your second month. Minimizing the damage is critical. The main reason for this strategy though is to provide you with considerable financial income at the start of each month. With each country that has a satellite, your income for each month will increase.
In light of the finances you will receive in the coming months, don't hesitate to sell off everything in the early months. Just accept that the first few months will be rough. Go to the Grey market and sell off all artifacts, corpses and UFO parts. Getting satellite coverage early will cost you a lot of space bucks so you will have to scrape together as much as you can. You will need money for power generators, excavation, elevators, satellite uplinks as well as workshops to provide you with additional engineers. Oh and don't forget to build the satellites as well. They take 20 days to make, try to have them ready before the end of the month. Also, build 4 of them at a time; they will all finish at the same time. Sell Elerium and Alloys if you must, but these are required to develop weapons and are very rare early on. Therefore it is easy for you to screw yourself over if you get rid of too much of these otherworldly resources. Having a shortage of these, especially weapon fragments, will halt the most important research in the early parts of the game.
Less “Bang Bang!” and more “Pew Pew!” - I'm talking about Beam weapons!
This brings me to my next point; what to research, or rather, in what order to tackle the research. What you will want to do is to make a straight beeline towards acquiring beam weapons asap. These will give you a significant boost to your offense as you replace your starter peashooter weapons. If you manage things correctly, you will be able to equip your troops with these civilized weapons surprisingly early, alleviating some of the difficulty at the start.
I'm sure you can figure out the rest of the base management on your own. Remember, don't rush the story, focus on getting a sturdy foundation first. With these bases covered (pun intended), I'm going to move on to the meat of the game and where the difficulty lies. Yes the turn based strategy skirmishes.
Strategy wins the day, educate yourself
The most important thing to keep in mind is to always try and leave as little as you can up to chance. Make an effort to set up favorable situations and remember that time is on your side.
Control visibility when moving around the map
This one may take a bit of explaining but hear me out, as it’s the single best advice I can give. When playing Xcom, the enemy won't engage you until you have woken them up. What does this mean? It means that if you haven't seen them, they won't drop in out of nowhere and kill you. Once a group of enemies is triggered, they will get a free turn where they scatter off to nearby cover in order to best murder you. They will however never engage you without you getting an opportunity to set up your defense first.
With this in mind there are a few things you can do to allow yourself maximum flexibility should you trigger a group of enemies.
・Never advance with a dash. If there is a chance there are enemies lurking ahead. You will need that extra move to set up your attack plan should enemies be triggered.
・Move your troops in a conga line. What the hell did I just say? Look, if you keep one guy on point moving forward, as long as you walk with the rest of your dudes in his footsteps, there is 0% chance they will trigger new enemies. In other words: One guy scouts ahead, if it's safe, everybody follows.
・Cover is everything. Never leave a soldier out of cover, ever, unless you have a controlled situation. Half cover isn't much either so consider using “Hunker down“ to maximize the defense of your soldier if an enemy has its sights on him.
・Be mindfull of what your enemies can see. If you have one man on point scouting the area ahead and he triggers a group of enemies, chances are this is the only guy they can see. This allows you to set up a trap. The enemy will try to engage this one guy, what you can do is you can either hunker down with him or move him slightly out of the enemy's sight. This will in most cases encourage the enemies to move in closer for a better shot, unaware that you have 5 other soldiers waiting for them in overwatch. This doesn't apply to all enemies of course, but it will always work on those pesky floaters.
With these points in mind, hopefully you will be able to advance slowly and not trigger too many enemies at once, allowing you to take your time and dispatch one group at a time.
Lets cover the classes quickly shall we?
Equip your rookies with grenades
Grenades are lovely, not only do they blow up your enemies with a satisfying bang - they are also incredibly reliable. Each grenade will always deal 3 points of damage to any given enemy. Always. It also doesn't hurt that they are 100% accurate as well, making them perfect for your in-experienced near-sighted rookies who can't hit anything. Grenades will help them earn their first kill.
Keep support classes around.
I can't name how many times these guys have saved the day. They can carry 3 medkits (after a few promotions), can revive fallen soldiers and last but not least; they can provide cover with smoke grenades. Also consider picking the suppression ability. Suppressing an enemy will lower its aim percentage and allow your guy to take a free overwatch shot should the enemy try to move. It's a good alternative to taking a low percentage shot since it will limit what the alien can do in its turn.
Know how to use snipers
Snipers are very unreliable at first, not being able to fire their main weapon after moving. Fortunately with the right abilities these eagle-eyed soldiers can be made into ultimate badasses.
・First off, pick Squad sight as your first ability. This will allow them to fire upon any enemy as long as your squad can see them. This means that as long as there is flat terrain, you could simply keep a sniper in the back to cover your whole squad, awesome. Oh but it doesn't end there.
・Later you can pick an ability called Gunslinger. This will make your snipers super good with pistols making them reliable front-line men as well. Effectively allowing them to move and shoot. Later on as you acquire the foundry for your base, you will be able to upgrade pistols making them incredibly reliable.
・Last but not least, the sniper will eventually get an ability which lets half-cover count as full cover making them the toughest sons of bitches you could ask for.
Keep a panic heavy around. What is a panic heavy? It's what I like to consider a heavy class unit with all abilities catered towards blowing stuff up with rocket-launchers. Much like the grenades, Rockets are very reliable. With the correct abilities, a heavy unit will be able to carry a total of 4 rockets, 2 normal ones and 2 shredder ones. Picking Bullet swarm in addition to this will allow them to fire their main weapon once before firing the rocket, sweet!
Make sure your assault classes have lightening reflexes. The assault class is an aggressive bastard with high critical chance and exceptional mobility, making them perfect for setting up flanks. Lightening reflexes allows them to dodge overwatch attacks with 100% accuracy making them the best scouts available. Add on top of that the fact that they have the most hit points of any soldier and you have yourself an immovable front-line tank. Just don't get too aggressive with your flanking; you may just end up triggering more enemies!
That's all I can think of for now. If you have any tips, please share them in the comments below.
Last but not least, I wish to share an amazing lets-play of Xcom. The commentor provides additional insight to the game as he tackles the hardest difficulty the game has to offer: Iron Man Imposible