oxygenO
whatever is comfortable for you.

Buster Friskers
I pull 'em up to my armpits.

Uncannyxman
The waistband should not go any higher than your navel. Also they should not go so high as to compact your penis and balls together. The purpose of boxers or boxer briefs is to have your junk have more room to move around and not be constricted.

kenny
Personally I pull them just above the "pubic area"

StudMuffin
whatever you feel good

Greg
I'd suggest not wearing them on your head, although there are no inherent health risks in that if that is your preference. In any case, you should definitely avoid wearing them on your feet as the risk of falling is increased considerably in people who choose that fashion statement. Both companies also may make socks. Those can be worn on the feet with relatively little danger, although I still advise against the head.

saucedtitts
Wear them higher to support your balls. But not too tight

Cooper
Just a little bit lower than you have your pants at.