Want 6 Pack Abs - Start with Warm up
Make sure that you warm up before you start doing anything. A good way to warm up is to focus on the area you are going to train. As an example, if you are going to do strength training for your legs, you can just warm up your legs and forget about your arms and other non related parts of your body.
It is also good to alternate upper and lower body workouts because while the upper body needs some time to rest, you can still work the lower body.