I was watching a South African television show yesterday afternoon called Show Me How. The interviewee was showing how to make an amigurumi snail. During her demonstration, she showed how to make an invisible decrease. Hmm, I haven't seen that before. I thought if I wrote about it here, I might remember how to do it next time I need it. And someone else might find it useful.
My usual method of decreasing is just to skip a stitch in the row below: