The only way to get better is to be consistent with proper mechanics and strive for perfection every pitch. Use your mind. Pitching is 90% mental and 10% physical. Your mind can be your greatest ally or your worst enemy. Start training it now to focus specifically on what you want it to focus on when you want it to focus. You should be practicing enough that mental focus becomes second nature so that during the season we can really get to work on game strategy.
Nothing is more important than a calm and collected pitcher who can offer her team an even keel in any situation. A pitcher who is totally in control of herself is totally in control of the batter and can make the other team do whatever she wants whenever she wants. This way she becomes a servant to her teammates allowing them to back her up by making the plays she and her catcher decide whenever they decide.
This will be a difficult endeavor. Pitching requires many many hours of PERFECT practice to be effective- this will not happen practicing only 2 days a week or practicing sloppily. You and your catcher will need to be watching for mechanics mistakes and making sure you are doing everything correctly because, I can not be there to help during the off season. Be your own mentor and be tough on yourself!! You can do anything you put your mind to. It is just a matter of how much you want it.