Say a player has a 46 Work Ethic. How many points will he probably improve by over time if he has Average potential in a certain category? What about if he has high or low potential in something?

Work Ethic is not related to a players potential what-so-ever. Work Ethic only comes in in how fast a player improves, not what their max potential is.

I view potentials as follows:
Low, less then 10
Medium 11-20
High 21+

Shoot, I thought average was usually 20 and high was 30... thats why i've been valuing guys too high

Medium/Normal potential is actually 6-20, but otherwise zhawks is right on.

Most medium potential guys improve 10-15 points, but there are a few who max out at just 6 or 7, and a few who improve 20.

Most of guys who you will be looking at on the upper end of average (18+) come in as "high" in the players thoughts email at the beginning of the years. Otherwise, they will be in that 7-18 range.

Depending on playing time, WE can stop someone from getting to their potential because the last point or two before the dreaded email is difficult to get, usually (and points after that email are very difficult as well, since there is still usually 1 or maybe 2 points for improvement).

Seems lately I've had a number of guys who came in with low potential stop improving ("got the e-mail") within 5 practices and with zero improvement.

Bottom line is every player is different but keep in mind low could be zero...if it is a critical category to you try to consider if the player would be fine if he did not improve at all (worst case), as nothing is guaranteed.