LONG TOSS and BANDS. and as for mechanics... depends on the position you play but long toss 3-4 times a week for 30 minutes and work your way up to 190 feet. and work on throwing on a line.
Start lifting weights with your arms & legs one day. The next day do long tosses (Throw them straight). Do this pattern and you will see you are throwing harder with less effort. Because now you are using your legs more then just using your arms.
do lots and lots of shoulder excersices with light plate weights and use restistance bands everytime before you throw to make sure u are good and stretched out.. then throw long for 30-45 minutes.. but keep the ball in the air until ur arm is completely loose before you start throwin it on a line. the guy above me has the right idea though. but jus take care of your arm and throw a lot!