Elite first basemen are generally very developed physically before getting to college. The biggest factor in evaluating a top first baseman is the ability to hit for power and drive runs in. Coaches evaluating a hitting skills video of a first baseman will look for a short, compact swing, quick bat speed, and a load or hitting mechanism that generates a lot of power. Fielding ability is not as important for a first baseman, as long as he can make the routine play on a regular basis.
The most important factor in recruiting for 1B is the ability to hit for power or for a high average. While a 1B recruit at these levels may not be as polished, he should definitely show the potential to hit for power at some point in the near future.
First basemen at this level will possess some qualities, but not all of high level athletes at this position. Regardless, this is an offensive position at this level.
Like many positions, size is lacking for players in this tier. If they do have good size, athleticism may be missing or power. It is very important for college level first baseman to hit for power and drive in runs. This may be projectable for players who end up at this level.