Some of the kids at the junior high school I help out at have asked how to improve their range. They are currently playing a piece that has them play a top-of-the-staff F and they all struggle with it, and half of them can't hit it at all.
The main thing I've told them is to practice often. I know many of them only play during band (which is about 20min of actual playing time) and don't take their horns home at all.
As far as actual exercises, I'm not sure what to get them started on. I showed them some simple long tone exersices, and talked to them about the importance of proper embouchure, breath support, and the dangers of using too much mouthpiece pressure. I also talked to them about lip slurs, but I'm not sure what to actually have them play since the stuff that I do myself starts above most of their max ranges.
Any advice on this is appreciated. :)