I’m officially not here for the duration (of what? Probably my life, unfortunately, judging by the amount of schoolwork I’ve got) but as a recent college applicant who got into the college of her choice, I just want to weigh in as I had a similar problem.
I applied to honors programs, where this was very important, but FFG is right, otherwise- if you have the SATs and grades, you’re in at many to most colleges. If your program is very competitive, then yes, this is something to worry about, I guess.
APs are a great idea, though if you’re in twelfth grade already it might be too late if you haven’t taken any yet (though you can certainly write down that you intend to take in May), and if you’re in beis midrash I’m not sure you’re eligible. CLEPs are good in that case, but probably not going to be considered advanced because they’re intended for high school graduates anyway.
In general, there are a lot of good ideas above. One of the first things my teacher told me when I started applying was to write down a list of EVERYTHING I’d done over the last three years and was likely to do this year and then put them into categories. I was able to put things I’d never really thought of as ECs down on that application feeling good about it. Tutoring, playing an instrument, public speaking at school events, being published- I’d never thought that could work.
Try to see what you’ve done and do now- EVERYTHING- and put it all into categories, like hobbies, school events, academic (were you on the honor roll? That counts too), volunteering, etc. Then devise a one-sentence explanation for each one that you think will make you sound unique.
If you’ve been sitting around your whole life playing basketball, then put down basketball as one of your extracurriculars, but there’s not much else you can do. There’s a reason why selective colleges WANT these things.
Hatzlacha!