Have a look at these two books:
http://blog.chess.com/farbror/paddy-patzers-pile-of-books-studying-chess-made-easy
Chess mentor has to be the best invention ever. That along with tactics trainers and all the computer workout courses.
Put a good chunk of hours into those as often as you can and it can only help you.
Record every game and go over it with your opponet and later with someone who plays better than you do, an expert would be even better.
One very useful approach is to avoid distractions. It's almost strange how difficult it is to actually be studying chess itself, instead of surfing web pages and posing questions about chess, for instance. I see there's a user on the front page right now who has posed completely inconsequential questions, four of them on the front page (!), in General Discussion about Chess - I would say that user is not studying chess in the proper way.
But it's also a question of perspective. Let's say you want to create chess pieces. Your study of chess would then involve examining prior experiences, the selecting and curing of wood, woodworking, design, etc.
My chief recommendation would be to consider any time not spent working on your repertoire and depth to be a complete waste. Maybe also work on tactics, instead of question posing skills.
I've been trying to properly study chess for some time now and my only conclusion so far is that what I'm currently doing (playing more games) is obviously not working.
I can see how practicing end games and memorizing openings can be considered "studying," but how about studyng general aspects of the game? How is it normally done?
Is it about visualizing ways to force moves using a knight and a rook, two bishops and a king, etc?