The "get a 2nd car" was really the best early game advice for a "x-com files" beginner, what a difference it made in my monthly score despite the random events.
I then added a 3rd hangar to my base to make a van (as it can transport 4 agents) for bigger missions that aren't too far from my base (as the van while having long range is really slow, so forget about reaching a mission location in the other side of the world before it disappear) so there's simply no way i could have a disappearing mission anymore.
This first april i reached a very good score, but i don't know why exactly (considering how low positive score you get from those apprehension and life form mission)
Though i got an undercover (in work suit) "capture the leader" mission but unfortunately my crowbars killed that leader (without much choice as he and his goons were all armed so i had not time to try to knock him out with how bad all the agents are at melee at that point of the game) so it probably didn't scored as good as it could have.
I think i probably got a positive random event, but i doubt it was a big positive score.
Maybe all the researches and interrogation are increasing the score like that ?
edit : after checking more closely it seems "life forms" mission score more than 100 points each at least, i haven't done such mission that ended with a capture only in killing the monster(s) . So looks like they're very good missions for the scoring.