This is an excellent question. I have played fantasy football for about 8 seasons now and I've won 3 of those seasons. It really is a lot of strategy, and luck combined. The last year that I won, which was 09, I only had one starter on my roster that I actually drafted. These leagues are won through the waiver wire. Adrian Peterson was the only player I had drafted, but I was able to pick up Kurt Warner on a trade, then got Miles Austin, Ray Rice, and Pierre Garcon off the waiver wire. This was the breakout year for those guys, so they weren't drafted cause no one knew about them.
It's also luck. Right now, I'm 2-1, only because the teams I play against have had horrible games. I've only scored 119 points in three games, which would typically get you an 0-3 record, but luck has prevailed and I've managed to outscore my opponents. It does make the football season more fun because you get involved in a lot more games than you normally would because you're following players from all over the league.
Hope this info helps!