Some of it is personal preference but there are some things you should do : 1) put a jacket on to keep your arm warm. 2) hydrate. 3) talk to your PC & catcher about who you will face next inning & how to pitch them. As for warm up pitches - 4 from the stretch and 4 from the windup. Half the pitches in every bullpen should be from the stretch as well. Learn your body and pay attention to what it says to you.