i wonder if the game creates the number of civilians in the ground battle map based on population density where you shot down the ufo?
then it would make sense to try to shoot down the ufo-s in less populated areas.
i mean, nations would certainly be happy if the ufo-s didn't crash in towns and cities with lots of civilian casualties.
I'd be surprised if the game kept that into account.
My feeling is that in 2.4 the first 2-3 months are particularly tough, after that it's getting better as you can afford building more bases that span more continents, get more missions, more cash, etc.
Like H-Hour says, jump on every mission you can, shoot down every scout and -if possible- every fighter. In the beginning I was hesitant to shoot down fighters since I didn't have the cash to loose too many aircraft; some nations dropped to neutral or even below in the first 2 months but I managed to crawl out of that hole, getting everyone to at least happy.
You'll indeed need more than 12 missions in 3 months... Do you have the cash to build at least some radars and SAM sites on other continents? Or even better, another base?