Aleister Crowley's text Liber III vel Jugorum hasn't been raised to its deserved "status". This technique created by him is one of the best techniques applied upon oneself, with results that are similar to practicing yoga. Crowley didn't make an effort to "spread" the message, he tried to keep his work only for the "chosen", but that's another story. What I intend is to do is put his ideas into a different perspective, one that is easier for everyone to understand and use.
His technique centre upon one self's speech control, body control, and mind control. Although these exercises may appear at first impression to be dumb, if one can't handle these seemingly pointless exercises, it is hard for such a person to really go anywhere in studying Magick. Only a short time after reading his text, I decided "bah! I'll just try it," and a few times after starting, I began to realize how deep it could reach. But that's up to each of us to decide if they want to try or not.
In each exercise you establish one "not to do" goal. Each time you fail in keeping up with your will, you punish yourself. Crowley's suggestion was for one to cut him/her self with a razor on the forearm, but you can also use a bracelet that stretches out, and then you let it snap back into your arm to make your body notice that you aren't keeping your word. Of course you may find a way to deal with punishing yourself that you prefer; Robert Anton Wilson, for example, was fond of giving his thumb a good hard bite. The critical ingredient is some form of painful negative reinforcement.
As for the exercises, Crowley also recommends doing them in sequence, and at the least, doing one in each week (at least... it takes three weeks). But that's up for each one of course.
You should choose one word that you aren't allowed to say. You can replace the word by a similar one or a paraphrase. Each time you say it, punish yourself. As a second exercise you can choose a letter, like "s" or "t". You can devise similar exercises.
First avoid lifting your left arm above the waist (at least for one week). Second exercise will be never to cross your legs. For similar exercises, you can, for instance, never put any of your hands into your pockets, or never to touch on your nose (yourself and your own, of course). Of course you can devise your own.
The first is to choose one thought to avoid. Basically each time you think about a chosen definite subject or anything in connection with it, punish yourself. This can be quiet surprising as you begin to feel your thoughts and to know exactly what are you thinking about and how you react to the "external" world. And this (for me) is the hardest one: choose two completely different personalities that you will be using at the same time (at least for one week). With a ring you choose the personality who is in command at the moment, that means that when the ring is in your left hand, personality A is in control, when you switch the ring to the other hand, personality B is in control. For instance one personality can be a nice person, always friendly to all, never drinking, always peaceful. The other one can be a bloodless thinker, someone who will only stop when stopped, someone very proud. Of course you can/should devise your own.
You should keep a diary so that you become more aware of yourself each day. When you start any exercise the first times it's hard to notice you are disrespecting your will, but with time you will stop before doing whatever you are intending not to do. When you are lazy and don't punish yourself when due, things will keep "biting" in your mind, it is preferable to just do it or give up the exercise entirely.
I recommend Crowley's stage approach too. It's easier and you are building different sides of yourself, but always strengthening your disciplined will.