In general you should be spending approximately 80% of your time practicing and 20% of your time studying.
Once you've practiced to the point that your skill plateaus, you should then study more often to improve your play through analysis of your own games/studying GM games/reading books/memorizing openings and endgames. This same formula works for pretty much anything you want to improve at, not just chess.
I remember seeing a while ago someone post the recommended percentage of time that should be devoted to playing chess versus studying it in order to improve depending on the rating of the individual. It was something to the effect that if you are rated over 2300 you should spend the majority of your time studying while if you are 1200 you should be spending the majority of your time playing. I have done a lot of internet and chess.com searches and simply cannot locate this percentage scheme. Does anyone happen to have the exact break down? I know it is individual dependent but I really would like to find these numbers again for whatever they are worth. Thank you!