Look up player stats and do a little bit of research before draft day, there are also cheat sheets that can help you too. It's all about the stats so look at those each week, and certain people win their leagues due to the waiver wire so be on the lookout for potential diamonds in the rough. Matchups are important on deciding who to start and sit. If you played fantasy basketball before you should have a good grasp on the fantasy game so it wouldn't be hard to transition over to football.
If you're jumping in cold, cheat and just print out cheat sheets and use them. I like: http://walterfootball.com/fantasy2012top250.php Google to look around. Important tip: look closely to see when they were updated. If they weren't updated in the last couple of days, move on. Tip #2: The NFL has changed tremendously over the last 10-15 years, and fantasy with it. It used to be a ironclad rule that you selected RB only the first two rounds, then a WR, then a QB, then BPA. That strategy is suicide today. Take care of your aerial attack. If you have a crack at Rodgers, Brady, Brees, Stafford, or even Newton....you do it. The only RBs you should take in the first are Foster, Rice, or McCoy (especially in an 8 team league). If they're gone, take a hard look at Calvin Johnson or Larry Fitzgerald. IMO, you should lock down two strong WRs before you go for a second RB. It's getting tougher to field a good stable of wideouts...but it's more important that you do that than worry about a 10 point RB2. After ~10-11 rounds, shift your attention to sleepers. There's not much gained taking a (real world) back up running back like DeAngelo Williams - you know already he's not going win you games. Take a chance on a rookie back instead - a lot of sites list sleeper prospects if you need help. If you missed out on the elite QBs, grab what vet you can but be certain to also snag a rookie or young guy like Luck, RG3, or Locker. Same reasoning. Kicker is your final pick. Unless you have a crack at a stud like the Texans, DST should be your second to last pick. If Gronk and Graham are off the board, don't be in a hurry for TE.