I'm going to start MMA...any advice?

You will get in shape, trust me on that. Be willing to learn. Pay very close attention to what they are showing you.

DO NOT say alright or you got it when you should either be tapping with your hand or saying out loud "Tap Tap"

Edit: I want to say I disagree with the poster above me saying get in shape first. Going down and getting thrown right in to it is an excelent and painfully great way to get in shape

I was in Kickboxing for a year then the shop closed down but its real fun if you have a big desire for it my only advice is lift weights get bulky because you dont want to be some skinny or fat guy in a ring with some guy who is more built then you are

so lift weights
train hard
dont be afraid
im 15 right now and were i went to go kickboxing i was the only kid their
i was sparring with guys who have been in the ring for a long time
and i got my ass kicked a lot and i knocked out 1 guy who is 10 years older then me which felt great but i was afraid and that is what made me loose my practice fight