Slipped under the first fret when not in use. I got in that habit...oh 25 or so years ago when I was a college student. Didn't have money to waste on lost picks. Anybody could play my guitar but they new damn well not to lose my pick! I don't think I've bought more than 100 picks since. At a gig I might have another handy on top of the amp but then I might not. I can count on one hand the number of times I've dropped a pick while on a gig.
I keep spares in the pockets of all my guitar cases, but usually end up using one that I stick between three strings.
At home, I keep them into a can of Altoids.