A young adult book, actually. It’s about 2 boys, maybe 13 or so, who throughout the course of the book go on a quest to learn how to “think” themselves into an alternate dimension. One of the boys has a special talent for tripping people in creative ways; in one scene he makes the class bully trip by waiting until he’s walking towards a trash can and giving a piercing whistle, causing the bully to turn his head sharply and veer into the can. I seem to remember a Zen-ish motorcycle gang, the leader of which aids the boys in their quest. IIRC, at the end it turns out the tripping boy is an alien. The only other thing I remember is that the non-tripping boy is new to the school; at the beginning of the book his teacher makes him stand up and do the dreaded “Tell us a little about yourself” spiel, and he reveals he spent the summer working in some kind of scrap-fabric place and he got fleas. I read it in the early 80s.
And heck, while we’re at it, post your own queries. Let’s make a night of it.