I'm assuming you are talking about cs stuff, but work on stuff that you enjoy doing. As obvious as that sounds, I wish I had spent more time learning cs before

I'm assuming you are talking about cs stuff, but work on stuff that you enjoy doing. As obvious as that sounds, I wish I had spent more time learning cs before I came to college. In fact, it is my biggest regret in terms of education. Of course I enjoy computer science immensely and I don't let this regret hinder me now that I am in college, but if there's any advice I think you should take at this moment, just work on stuff you enjoy. If you play video games, write a mod/cheat for them, or even server host if the game you play allows for it. I am NOT saying to use the cheat to win, but the knowledge you gain from writing one is invaluable if you find it interesting, and the same applies for modding/server hosting. Having played a ton of video games in high school, especially counter strike, I knew a ton of people that hosted servers and wrote cheats, and I personally think it's the best pipeline to being cracked at cs, specifically my friends that developed cheats. If you have an interest in ML, train a model to make market predictions. None of these projects need to be fully flushed out, but its a good conversation piece and employers like seeing self-driven development. You only get less free time the older you get, so get started early! Also enjoy high school, don't let your work consume you.