Welcome aboard Skip!
Another thing to think about is your periscope. Don't leave it up for long periods, look in little peeks.
As has already been said, get into position as easrly as possible, and let the enemy come to you. That way you can go deep and even come to all stop, so you make effectively no noise.
You have to be stealthy and hit hard, seemingly from out of nowhere! Think of yourself as a sniper.
Good Hunting
