+1

When I did my flight training, I was told to use the Valsalva manoeuvre and it works well in my experience (unless you're flying in an unpressurised plane with a cold... which you learn not to do again). However, I'd advise not to exhale too hard as it could obviously lead to some sort of ear damage. I generally try moving my jaw or swallowing and if it isn't working, I use the Valsalva manoeuvre, by firmly exhaling through my nose. Don't "force" it as if you were sneezing, that can only lead to bad things.