I can add a bit on insight here, as I was the lead vocalist and guitar player in a rock band for 10 years. Honestly, it really helped to inform my voice acting.
1. Always warm up. It goes without saying, but I'm surprised that a few folks miss this important step.
2. Relax. Tension is the enemy here. You'd be surprised how well you can scream without holding tension in your body. Remember, don't push it out!
3. Hydrate. Also a no brainer, but for ANY type of voice work you need to stay hydrated. This means start drinking (water, people. Water.) the day before and/or all day leading up to the session. My gauge was the "clear urine" test. If you can see through yer' pee, you're doing good.
4. Enjoy something like "Throat Coat Tea" throughout the session. Helps to lubricate and sooth inflammation.
5. After the session, rest those 'chords. Refrain from speaking, and if you do speak in a normal volume. Whispering can be strenuous believe it or not.
6. Rest. Before and after the session, get plenty of rest. All of your body's systems are intricately connected and a well rested body is a happy one and less succeptible to injury. Don't rush into the session on 3 hours sleep. Get a good night of sleep afterward too, especially if you have to go in the next day and do it all again.
I know its late advice to the party, but hope that helps!