One of the mistakes I most often see fantasy owners make in keeper leagues is keeping players who were studs the year before, but also cost high draft picks to keep. This is a problematic strategy for a few reasons, not the least of which is the annual attrition that takes place amongst the “studs” of fantasy football.
The easiest way for me to describe my priority order when deciding on my keepers is through a simple matrix where the production of a player is shown across the top (low, moderate, high) and the draft pick cost is down the side (early round, mid-round, late round). In the boxes of the matrix I have put a number that corresponds with my priority for that action. So keeping a high production late rounder (Michael Vick) is the #1 priority.
Think of the production levels as being something like a high production guy is your typical fantasy stud, while a moderate production guy would be a guy who would start most weeks in your league. Maybe LeGarrette Blount is a good example.