7. Only launch satellites at the end of the month. They're the only way that you can directly affect a country's panic level and it's better to wait to see at the end of the month how the Panic levels are doing after the abductions. Also, some countries will offer you money if you have an undeployed satellite to have it patrolling their airspace.
8. When you start and until you encounter the aliens, move your squad as a whole during the 1st and 2nd Action - first action everyone moves together, then everyone Overwatches for the 2nd. Also keep them together so that you won't activate more than 1 group of enemies at the beginning.
9. Usually, never Overwatch until everyone is finished moving. Otherwise you might uncover any aliens and if soldiers already on Overwatch see them, they'll fire immediately and not fire during the alien's turn.
10. You can also use the above as a tactic (a risky one, but I've used it), if you know where a group of aliens is. Just place everyone out of their sight around them on Overwatch and send the last soldier to activate them. When they break for cover your overwatch soldiers will fire at them as they are scurrying for cover. The risk is that you might not kill anyone and you'll have no actions left when the aliens play. But it's a great show
11. Once a soldier gets promoted to Colonel he's off duty for routine missions. This forces you not to get used/dependent to the same team (with the catastrophic effects when you lose 1 or more), opens 1 slot for another soldier to get combat experience and prevents your Colonels from getting killed by bad luck on Abduction/Council missions or from taking Critical Wounds that lower their will.
12. Your first Colonel should be a Support Medic - the longer you keep your soldiers alive, the more they'll get promoted and gain experience.
13. Reload, reload, reload. If you have nothing to do with your unit, reload his weapon. Be always on the lookout for the squad ammo levels or you may find yourself in trouble.
14. Be very, very careful with Ghost Armor on an Assault class with the Close Quarters Specialist skill. Even if you have no actions left your soldier will fire (and lose invisibility) if any enemy unit comes within 4 tiles. This can mean that your Assault can fire, reveal itself and be killed by the rest of the aliens now that they know where he is.
15. There's two great ways to get rid of Sectopods without risking being exposed to their fire: Sniper with Squad Sight and Plasma Sniper Rifle (and take shots at it until it falls). Or 2 Assaults with Alloy Cannons, Rapid Fire and Ghost Armor - the two Assaults can bring down a Sectopod in 1 round with 4 cannon shots. If you don't have Ghost Armor use Lightning Reflexes or the Sectopod's Overwatch shot can kill your soldiers.