Begin a serious fitness program. You should work to improve your strength, endurance, speed and overall flexibility. Training your body appropriately can improve your athletic performance and help you perform on the field. If you can, choose to work out in your school's own gymnasium. Trainers and coaches are likely to be around, and may take notice of your hard work and see your dedication to improving.
Maintain a healthy diet. Ensuring that you receive proper nutrition each day not only provides fuel for your daily workouts, but it will also help you gain muscle and build overall strength. Poor diets sap your body of essential nutrients and degrade your athletic ability by promoting the development of fat cells. Nutrition is the key to maximizing the impact of your hard work.
Practice your chosen sport as much as time allows. If you're truly dedicated to making the varsity team, you must make sure your skills are growing to match those of your competitors. Whether it's taking extra batting practice, throwing footballs through a target or golfing more on the weekends, extra practice beyond what's required by your current team can help you outmatch your current teammates and ensure you move to varsity quicker.
Build a relationship with players on your school's varsity team. Ask them how they gained the skills to succeed at such a high level and how they prepare for each game or match. Furthermore, see if you can participate in extra practices or scrimmages with them. Playing your sport against better competitors not only improves your game, but it can prepare you mentally for your promotion to the varsity level.
Lobby the varsity team's coach to give you a chance on the team. Write a formal letter outlining the additional steps you've been taking to improve your game. With any luck, the coach has already noticed your extra work in the weight room or on the practice field, and has heard positive references from his other varsity players. Offer to go through a tryout if necessary to prove you are ready to progress to the varsity team.