For league bowling, practice last for 10 mins long. It is also called shadow bowling for some bowlers. Make sure you get to the bowling alley in time for practice. If your league starts at 6:30 then practice or shadow bowling starts at 6:20 for that league. With shadow, you can get warmed up and see how to lanes are and see how your bowling do on those lanes. Shadow bowling is very much needed before league play.