Heres some stuff I tend to do. I will never pick up a FAs until the season actually starts so that way the AI gets the best FAs out there. Also if I see a FA who is good and not picked up I'll trade him to a team who needs that position.
Depending on how my team looks I'll end up trading away my 1st round picks to the teams with lower rating/records. I usually sign players to 4-5 year contracts, and once that's up I don't resign them usually unless it's something amazing. Other then that I'll trade those players to weak teams.
That's all I can think for now lol So it seems like I always keep my teams fresh everywhere removing players, and adding rookies or low overall players who I want to make pro bowlers

now what about you