In high school + middle school, apply to EVERY competition. I don't mean HOSA, etc. but actual science competitions & awards. There are dozens of grants and scholarships every year and it's a hassle to apply, get recs, etc. But when you look at your peers who have so many awards and wins, it's not because they are necessarily better than you. A big piece is that if you apply to 10 contests, you might win 2.
Then, using those old awards, you can snowball into more and more.