What sort of pre-writing have you used succesfully in the past?

When I was in my sophomore year in high school we were taught how to do pre-writes. I used to hate writing pre writes. I felt that it was pointless and a waste of time. My teacher used to always say "do a pre write. Do a pre-write." I never understood why. Then one day I was asked to write an essay, I don't remember what the topic was or anything. But I distinctly remember starting the way we were supposed to, with a pre-write. So, when I first heard the topic, I had no idea what to chose. So I just chose something random and I thought I would have a lot of supports for. But, once I got started on my pre-write or outline, I found out that I had no idea what exactly to say on that topic. I could have continued writing that topic my I would have had to big deep to find details on it. So, I decided to chose a different topic. Not only did the pre-write help[ me know that I shouldn't do that topic. but, it also gave me ideas for a different topic to write about. After that I decided I need to do a pre-write every time and on everything. I even kind of do a pre-write on poems. Poems that I am assignment to do in school and stuff. It really helps me get my ideas flowing and helps me get excited about writing on that topic.