What is a good amount of time to leave for rest between workouts?
Basically, this depends on what sort of workout you are completing and how hard it is. If the training is for endurance purposes, then you can complete another workout after just 3 hours. If you are training for big muscles, then 48 hours is the minimum, and you can leave up to two weeks between workouts if training for strength.
Basically, you should leave a minimum of 3 days if weight training and 24 hours for cardio, but this will depend on a number of factors.