Had another play through (not quite finished) with the extended options after a first finish. There's a few VERY interesting options (extend game being the most interesting imo) that make a second play through rather different.
Ended up completely skipping laser development and got straight into plasma just as I started meeting the bulk of the mutons/cyberdiscs etc. Lost 1 country (Germany) but otherwise squeaked through.
Tips wise:
You MUST put all efforts into getting enough engineers to build more satellite uplinks until you can safely finish 1 per month. Make sure they are in a 2x2 formation so you get 4 free satellite slots (1 free per adjacent facility, it you do this, you don't need to bother with the nexus buildings).
Save your satellites until a day before the council, you'll often get a mission that will allow you to reduce panic in certain regions. You then launch sat's at the countries that will otherwise bail.
Be aware that even if a COUNTRY has low panic, doing a mission there reduces panic over the WHOLE AREA. So if e.g France is bricking it and about to leave, UK is happy and at 0 panic and you get an abduction mission choice with UK as an option, take it. France will reduce too.
South America or Africa are probably the best places for home base. Africa gives more cash. SA gives instant alien autopsy's and interrogations which generally give you research credits towards tech (e.g getting a live big green guy will cut plasma research time almost in half).
For tacticals: Move the tactical guys first into the best cover. Overlap each move where possible (so sprint one guy, move the other) don't shoot with the dude you move though. If anything is triggered you then have a full range of options for gunning them down. Generally move as: Tactical, Heavy, Sniper, Assault. The assaults with the run and gun option can be used to pull asses out of the fire if anyone gets badly flanked from triggering a pack you didn't see. Once you get plasma weapons giving the plasma rifles to your assaults gives you FRACTIONALLY less stopping power with far greater options for position, cover and covering fire. Once you get the options available I usually run with 2x tactical (one setup for suppression, one as medic) 2x assault (with a balance of defensive and offensive talents, the "shoot anything that comes close" option is amazeballs) 1x heavy, 1x sniper.
I don't THINK there's any spoilers in there.