If you are a neophyte then rather then rankings I would suggest finding a good ADP list. Then just go down it and mark who you like more or less then their average draft position. http://fantasyfootballcalculator.com/adp.php
is pretty good for that, as is ESPN.
Find a good tier list from ESPN, FFToolbox or whoever and then compare that to the ADP list. if you see a guy in a tier going 20 spots above or below the rest of that tier then thats a guy to target or avoid.
Remember, most rankings are based on projected point totals, one touchdown or two could move a guy 5-10 spots on a WR or RB list.
Knowing your league rules is the best way to judge. If you only start 2rb and 3 WR, with PPR and no flex then you want to take WR higher then theyve been going.