Make sure to loosen up your muscles before you engage in weight lifting. Stretching the muscle you are going to lift should be standard practice for everybody. If you are under 40, a 30 second stretch is adequate. However, if you are over 40, then you may want to stretch longer.
Jump rope is a fantastic calorie burner that you can do even when the weather is bad. If normal jump rope is too easy, try doing double jumps- jump twice as high and swing the rope quickly so that it clears your feet twice before you land. This is a very time-and-space-effective exercise that promotes cardiovascular health.
Exercising with groups of people can inspire you to reach new heights. This is helpful because a social group can motivate a person to go above and beyond what their normal goals would be when alone. The dynamic of having other people rely upon you, or at least to share your success with will definitely be a positive benefit on your fitness.