How do you guys level scopes?

[centerfire]

Scope caps are not square to the erector or the reticle. Square the bottom of the scope to the mounting base (Pic rail in this case), I use feeler gages but there's tons of ways to do it including a deck of cards. Once the scope is square to the rail go shoot the rifle. Scope mounted bubble levels are largely worthless and a waste of time. If you're concerned the reticle isn't square to the erector you'll need to shoot a tall target to tell how far out it is (unless it's visually noticeable).