One of the key players in the mental game in gymnastics is being able visualize the skills or routines you will be doing. Understanding what the skills look like, and what your body needs to do in order to make them look that, can have a major, positive impact in the way you learn new skills and maintain old ones.
Most coaches encourage their gymnasts to learn this ability by having them close their eyes and imagine themselves performing the skills or routines perfectly. This method can be highly effective, as it often addresses feelings of fear and confidence. However, I feel that it might be too passive to get a good grasp on the techniques of a skill. Artistic gymnasts can see themselves doing a trick correctly, but they might not know what exactly makes it done right.
Here's where I'd like to propose a new twist to mental visualization, one that will work best for single skills or short sequences. Rather than closing your eyes and thinking about the skill, get out a sheet of paper and a pencil. Let's use a back extension roll as an example. Think about what it looks like, from start to finish. Ask yourself: what are the important points in the back extension roll? What should my body look like? Are my legs and arms supposed to be bent or straight? When do I shoot for the handstand? How should the handstand look? How should I step out? How should I finish? Is my leotard suitable?
When you've thought about it, draw yourself doing the trick in a sequence of figures. They don't have to be perfect drawings. You don't even need to be a skilled artist. Stick figures work just fine. As you draw, pay attention to those points you thought about earlier. Make an effort to draw them clearly, and maybe even ask yourself why they should be that way (i.e. why should my arms be straight?). Pay attention to form as well.
When you have finished, take a good look at it. Does it look like the skill you are working on? Is there anything you see wrong with the form or technique? If there is something not quite right, don't despair! Fix it. Being able to pick out what's wrong when you look at a skill is an important ability to have, so you can know what not to do.
This method of visualization gives you more of an active role in understanding what is required of you. You can, first-hand, get a good grasp of how the skill works, how your body moves, and special techniques that make it easier.
When you have the sequence drawn right, study it. Memorize it, if you can. And next time you go to work on that skill, remember what you drew and apply it to yourself. With luck and practice, you'll have gained powerful insight into your gymnastics.