One of the biggest keys to success for an athlete is consistency. If you dedicate three or more days a week to training, then after a couple of months, you're going to see noticeable improvement in your abilities as a basketball player.
During the season, you have a lot of responsibilities that require your focus and energy, so the off-season is the perfect time to work on your weaknesses to develop your game. The first step with any program is figuring out what you're going to work on. (Try Oak Hill Academy Pre-Season Basketball Workout Program.) Make a list of your weakness, how you think you can cure them, and the goals you want to achieve before the next season. Once that's done, get in the gym and put in the work to becoming a better player.
Just do your best to stay committed and work hard every day. Use this great workout plan, which I designed for my high school team a couple of years ago and that helped them beat the 12th-ranked team in the nation.
Note: It's best to lift with a partner—for safety as well as to motivate each other to work harder.
Basketball Ball Handling Drills
Basketball Shooting Drills
Basketball Passing Drills
Basketball Rebounding Drills
Basketball Finishing Drills