Lots of great advice here, body weight plyometrics are great ways to develop strength and power. Weight training is another option but I would not advise it unless you are supervised for proper technique and that may be hard at home. Please do not neglect the hitting and throwing prep. Remember if you can throw gas or mash, they will find room for you on the team. Lastly one of the old timers made a great statement about team practices...it is not to make you better, it is an opportunity for you to show your coaches how much better you got.