At our draft position (8 +/-1) I would select someone who we expect to be on the field for all/most of the Offensive/Defensive plays, an impact player who should be starting by the 3'rd game, at a position that has an expectancy of 8 years. ie not RB, WR, S
There are always exceptions, we took Irving Fryar with the first pick in the '84 NFL draft, however I would limit my selection options to the following positions.
for a top-10 pick: QB, OT, TE, DE, Hybrid DE/LB, or CB. (No RB, WR, OG, OC, DT, MLB, S)
for a top-20 pick: QB, OT/G, TE, DE, Hybrid DE/LB, or DB. (No RB, WR, OC, MLB)
My preference for the #8 draft pick: TE, Hybrid DE/LB, or CB.