1. I can't remember the exact number folks say (21 maybe?), but I have always tried for 22 in the regular season and never had an issue.
2. As a rough ballpark figure, calculate 80 percent of the promised minutes amount and plan initially to aim at that. Each player is different -- some will be content with less than 80 percent, some will demand more. If you're running on the short side of the promise, keep a watch on the player's WE -- it will drop a single point if the kid thinks he's being shorted and you can calculate based off the kid's MPG and the promise where his personal percentage for happiness is. If you miss the first drop, the kid will send an email complaining and telling you how many additional minutes he thinks he should get. This will be accompanied by a second WE drop. At that point, meet the additional demand to regain the lost WE. Failure to do so risks losing the player at season's end.