Tips for baseball please, thanks! ?

I have not played baseball in about 3 years. I used to play outfield and 3rd base but I wasnt too good at them because I wasnt very aggressive, and also, I was overweight (I was 13 Ish). Now that I am older I am perfect weight and in very good shape and because of this my competitiveness has gone up tremendously and I am now very serious about sports I play. My favorite sport has always been baseball and recently while I was throwing with a friend to mess around I was gunning the ball like if I was playing third, and i am also more agile now. My school coach saw me and wants me to tryout next year. I am 16, 5'11" and weigh 170, haven't played baseball for a league in 3 years, and am expected to tryout as if Ive been playing currently. Tryouts are iin febrauary of 2012. What should i do to be sure to make the team next year? This sounds ridiculous I know, but I just dont know where to start.