If you want to check it in the field, or don't have a swingarm stand, I've found this method to feel reasonably safe:
With the bike on it's sidestand, squat on the right side of the bike. Grab the handgrip_and_the front brake with your right hand, grab the frame or footpeg bracket with your left hand. Gently tilt the bike towards you. It's easy to feel when it gets close to the balance point. Inspect oil level, and gently lean it back onto the sidestand.
Of course, if you have the auto-retract sidestand, this method is not so good....