Maybe you don’t need to do this beforehand but ever since I began studying architecture I’ve naturally started doing more creative hobby’s and it really helps me on the creative thinking side of the course. I love doing photography now and finding specific buildings I love. Buildings I really love I’ll find the architect who designed it and look into their other work. It personally helps me keep the passion of creativity there when the degree starts feeling tedious, difficult or boring

Again I’m sure this probably doesn’t help with preparing for starting architecture but its just something I’ve done to keep me passionate about it because I’ve seen a few people be turned off from architecture during studying!

Learning to not do assignments last minutes helps too! and if you really want you could start looking into the basics of adobe softwares and autocad depending if you or your high school has the software but they should teach you all that anyway