From the Book of Duh: Hold the front brake on while balancing the bike level to look at the sight glass. Since you're kneeling down doing this it's hard enough to hold the bike side-to-side. This way you don't also have to worry about it rolling away.
Steelheart- '03 Speedmaster Black/Yellow
The Hayabusa Killa
16" Shorties/140 mains/Airbox drilled
Procom CDI
"There is no cure for Celibacy. But we can treat the symptoms."