New To High School Ball

While velocity is important don't fall in love with it. The ability to throw strikes consistently is what matters most.

The absolute best way to increase velocity is to long toss as much as possible. Make sure you don't end up throwing with poor mechanics and do damage to your arm.

Throw it far, don't launch it far.

Google search 'building a cannon arm' and you should be directed to junior baseball skills. There is a weight program for youth baseball players which give you 8-10 recommended arm exercises. I'd suggest trying this along with a supervised long toss program. As coach2709, says, "Throw it far, don't launch it far." Long toss should not be overdone, but is critical in achieving arm strength.

Long toss and perfecting your mechanics are 2 of the most important things you can do to increase velocity. As for weight training, I'd start with lower body exercises, leg strength is very important in pitching. I'd be careful with the upper body, as injuries from lifting, especially if you have little experience, can be common. I'd suggest posting something in the strength and conditioning forum.