What to med school's look at for admission other than the MCAT?

Depends where in world you want to go to your med school.  In Canada they look at volunteering, extra-curricular activities, your university marks, MCAT, and the most important is the interview process (if you get through the first filtering stage).  I'm pretty sure it's the same thing in the USA.  In the Caribbean med schools (as an example, I went there), they are not really fussy about volunteer work or extracurriculars, but some schools still require MCAT, and some don't.  But interview is still there, even though it's not as thorough as the one in Canada or USA.
Do well in high school, university will be easier that way, and make good connections with the professors at the university you'll attend... reference letters are very important too, and you can get volunteer experience or even more with the professors
All the best!

In the UK, relevant voluntary work is essential; although they won't always say they require it, you won't get an interview without it... (That or be of a high social status as is the norm for older doctors like the ones that will be doing the interviews.) I can't say much for US admissions, but either way, it can't do any harm, even if it is a pain.

College GPA, amount and difficulty of college coursework, and perhaps most important, your activities outside of the classroom.  

- Find a leadership position (club, work, etc; doctors are usually in charge when they work, they want to know you can handle that)
- Volunteer doing something you're passionate about (they want giving people; they will expect you to give your life to medicine)
- Do some research (understanding of how scientific knowledge is acquired)
- Shadow a doctor (they want to know that you understand what you're getting into)
- Work or volunteer in a medically related setting (same reason as shadowing)


Medical schools have general criteria when they look at applicants.  First, they want to know if you're smart enough to handle the curriculum at medical school (MCAT).  Second, they want to know if you're hard working and consistent (GPA and academic record; letters of recommendation).  Third, they want to know that you understand the field you're choosing to enter (shadowing, medically related volunteering, even experiences with someone who has a chronic illness).  Fourth, they want to know if you're interesting and have something to offer their school outside of medicine (personal statement, secondary essays; talk about hobbies, what you do outside of school, why you do it, why it has impacted your decision to enter medicine, and how it relates to your abilities as a potential physician).  Fifth, they want to make sure that they can stand you for four years.  This is the purpose of the interview.  If you get that far, all you have to do is not screw up.  

At your level there are a few things that you can do if you are sure you want to be a physician (or at least sure enough to start getting prepared now):
- Increase you academic competence (take hard classes like chemistry, physics, calculus, philosophy, critical thinking, etc)
- Find activities outside of school that you can be consistent with (a job, volunteering, a sport, etc)
- Find activities related to medicine (volunteer at a hospital, the VA, or in a variety of settings that expose you to patient contact)
- Get experience in leadership (join a club and aim for an officer role; be creative, there are many ways to act as a leader)
- Work on getting into the best college you can


Some essential resources for any aspiring physician:
http://www.aspiringdocs.org/site/c.luIUL9MUJtE/b.2011035/k.C6A4/WELCOME/apps/lk/content3.aspx
http://amsa.org/AMSA/Homepage/MemberCenter/ForPremedicalStudents.aspx
http://www.studentdoctor.net/
http://aamc.org/