Might be obvious, but see what topics or broad subjects you like or dislike and use them to narrow down your options. Also applies to skills or processes. If you enjoy creating something from scratch or solving problems for example, that could help you decide on a career or category of careers you'd have fun (or at least not dread) doing. For an admittedly extreme example I've been set on engineering since sixth grade not because I had some pre-existing passion for R&D or building stuff, but because I liked math and science (but not biology, fuck biology) and hated memorization (and humanities pretty much by extension). If you don't have the information about yourself to choose these kinds of criteria, then you should try new stuff until you do. This could be coding, a new language or even sewing or whatever, but the best way to get to know yourself is to expose yourself to new things and see what sticks and what doesn't.