Please help aspiring to-be-doctor. I would like to take all the advice.
Current 8th grade - Geometry honors
Redcross Volunteer
Robotics FTC member
member of local swim team.
Plays violin (not a part of Orchestra)
Member of Rocketry team.
Outgoing senior here. Congrats! Welcome to high school!
Chill out. You're a freshman! You have four years to decide what you want to do in college and once there, four more years to decide if you want to go to med school at all.
Don't build yourself for one school. This is important. Any program that involves medical school is super competitive let alone one run by Brown, not to mention it may not be your best option. Look at these statistics for 2015: Number of applicants to PLME - 2447. Number offered admission to PLME - 90. That is a 4% acceptance rate. Do NOT go into high school with the mindset that your one goal in life is this school and that your entire transcript is made to cater to it. You'll be miserable.
Volunteer and see what you can do. You are probably too young right now to participate in volunteer work in hospitals and similar settings but that is OK. High school is not when you should be treating patients - it's when you should be discovering if you enjoy something.
Keep your grades up. Geometry honors is great! Make sure you absolutely keep that up and to maintain a high GPA. Build an extremely strong foundation in math - you'll need it for stats and calculus.
Plan your AP courses. This is general in case premed isnt what you want or your major is not bio/chem. AP courses are more challenging, schools like them, and they can save you money when you skip intro courses in college. However, keep in mind this: it is not advisable to skip premed courses with AP credit so don't plan too much to use AP Chemistry to skip intro to Chem and go directly into organic chemistry.
Chill. Your extracurriculars look fine. Join whatever you want and find your passion. Do it well but have fun doing it. Remember: high school is important but it is not a "if you fail you're screwed!" type of deal. The worst thing you can do is burn yourself out in freshman year of high school doing things you dont enjoy.
The only thing that high school students need to be aware of specifically for pre-med is that college courses taken while in high school will affect the college GPAs calculated for applying to medical school, so consider that carefully if you are offered the option of taking college courses while in high school (dual enrollment or otherwise; earning A grades is obviously good at preloading your college GPA, but earning B+ or lower grades is bad for pre-med purposes).
Otherwise, the usual recommendation for college-prep high school students applies: choose a well rounded base of high school course work, choose high level (e.g. honors or AP or whatever) options (particularly in math, science, and English), and do well in all of your courses.