Set the tempdb data and log files to the size they need to be.  That'll be the size they've grown to, so don't shrink them.  Don't create extra log files - there is no performance benefit.  Only create extra data files if you're seeing IAM page latch contention.  If you're doing index maintenance overnight, don't stop backing up the log at 4pm.  And, as I and others have already said, fix the code if it's in your power to do so.

John