If you are interested in getting the very finest results out of weight training, work out each arm and leg individually. While this takes much longer than exercises that use the arms or legs together, the overall benefits are superior. Concentrating on just one limb provides improved muscle tone and faster muscle growth.
The most important part of any fitness program is consistency. Instead of pushing yourself and hating it once every few weeks and then going back to being sedentary, make a regular exercise program and stick to it. 20 minutes on the treadmill three times a week makes a much bigger difference than an hour once a month, and it's easier, too.