1. Warm Up - Duh, you say, but you do it all the time, admit it! You get right to running, or dancing, or playing hockey without warming up. Five minutes of working up to a light sweat can save you.
2. Get a Buddy - Weight training is much safer and more fun when you have a spotter. You'll be able to push yourself much harder if you've got someone to watch your back.
3. Get Good Shoes - You may have gotten away with lifting in your Keds when you were young, but the older you get the more important it becomes to wear the best shoes you can. The feet support the whole system so take care of them.
4. Crosstrain - Overuse injuries may be prevented when you mix things up. Besides, variety makes for better workouts and keeps boredom at bay.
5. Cool Down - Again, it's five minutes out of your life. Take a few minutes to settle down before you stop. Let your body temperature cool off and the heart rate come down with some moderate movement. Then remember to stretch to avoid sore muscles later.