During the free agent signing period in Franchise mode, you can offer a relatively low salary to any free agent. If they have no offers besides yours at the end of the signing period, they will sign with you.
This trick will work for almost any created players with pretty low speed in Road To The Show mode. When on third base, take as many steps as you can off the bag. As soon as you see the "Step Back" button flash yellow repeatedly, tap R1. This will cause your player to bolt for home plate. Continue to tap R1. Because you are already three steps off the base by the time the third baseman throws it to home, you will already be safe. This works about 90% of the time, and you will not even have to dive.
If you have a fast base runner such as Jacoby Ellsbury, Chone Figgins, Ichrio, etc., steal most of the time to second or third with speed all the way up. Have a decenthitter at the plate to score easy runs.