It's rather simple. Fly as best as you can, get a more than positive K/D/A ratio (like 15-6-3 plus some AI kills when they're in sight), have the highest dmg on cap ships of all players, ideal would be also if you solo some subsystems, be amongst the 3 top scorers if not the highest scoring player in the match.
If you hit all this criteria you will only lose a bit of rank when, the rest of your team consists of brain dead feeders ending with close to 20 deaths each and losing the game for you.
To gain rank- just pray to rng-sus that he might spare you from such "teammates" so your performance won't be completely irrelevant...
Seems like a lot of matches are one person doing the work while others are just doing whatever passes into their sites. Deliberately crashing into obstacles when they are about to get waxed (pilot error) or just doing weird random stuff instead of objectives. Fleet battles has strong emphasis on team work, but rarely actually see it. Rank system is rubbish at the moment, I've stopped looking at it because it only adds frustration.
