u know, im considering the same thing- so i feel it necessary for me to throw in my two cents.
in high school i was insanely involved in Mock Trial...i went to a law and government magnet high school, and mock trial was second to religion in the magnet...we placed in the top 3 three out of the 4 years i was in the mock trial program.
but i have to honestly say that as i look back, i sort of regret the time and energy i devoted to mock trial. sure, i learned a lot of things, things that werent taught in the classroom and such- but u have to take into consideration the opportunity cost of being on the mock trial team. i personally believe that if i had taken the time that i spent in mock trial, and did some other activity(s), i would have been more successful in the college admissions process. unless you're going to be the team captain for the national championship mock trial team, perhaps look into other less generic clubs that might set you apart from the pack. there are tons of students across the country that do mock trial, so it might be in your best interest to do something more suited to your tastes. as ariestara said on a previous thread, law school admissions seems like its become the evaluation of poli sci majors...and while it is true that if you're an excellent political science student, or mock trial participant- you will be rewarded....but if not, why not do something that rewards the time you devote to mock trial? I'm 100% sure that if you start some sort of original club or activity that reflects your personality or your life's goals- you'll be in a much better position than some mock trialer. Remember, in the arena of competition, especially in the country we live in- nobody remembers second or third place. So unless you're going to be the best at it, i suggest doing something else.
i dunno, i may be off on this whole subject...just wanted to share a bit of information that i wish i had known a little sooner...but o well...the friendships and experiences i learned in mock trial will forever be remembered, so...i guess u should just take what i said with a grain of salt, but keep it in mind before you jump into mock trial and devote 20 hours out of the week writing your cross-examinations.