1. Always stretch before workouts - Try touching your toes, doing a split as far as you can go and stretching your arms, pulling your leg to touch your butt.
2. Always try to do cardio - if you are now starting do at least 1 week cardio (running, biking, walking, etc.) before training with the weights. I would reccommend a 20-30 mins running before muscle building training.
3. Always drink fluids, water, etc.
4. Stretch after workout.
These are a few tips my friend and I do when we go to the gym. 1 last thing know your limits don't push yourself too hard to the point where you pull a muscle there's always tommorrow.
Hope this helps and good luck with your training mate