How do you level your turntable?

A 9" "torpedo" bubble level works great. $4-5 dollars at Lowes or Home depo. A torpedo level gives you a north-south, east-west and diagonal level reading at the same time.

Actually, a 9' torpedo oughta level things very well. ;-)

I use digital level with great result. You can actually level to zero degree with digital level. It only gives approximate indication (hardly to zero) with bubble level. You hear the difference when you level your platter to zero degree.

I use a bubble level on the plinth, not the platter.

The plinth is not necessarily in line with the platter unless you have confirmed that it is.