How do you level your turntable?

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.

Just a newbie and still working on setting my my first (real) turntable, I thought I would just put in my $0.02. Being a carpenter with extensive experience with levels, I just wanted to point out the proper use of a bubble level. Although it looks pretty simple and straight forward, it is very important that you read it correctly. Most levels have a bubble that is smaller than the lines it is to be centered in. Just because the bubble is "inside the lines", that does not mean it is level. The bubble must have EXACT spacing from the edge of the bubble to the corresponding line otherwise it will not be level. I have also seen levels where the bubble is wider than the two lines. Here you need to be sure the overhanging bubble is equally hanging over the lines. In either case, you will be surprised as to how much out of level your turntable will be if this proceedure is not followed. From all that I have been reading on setting up a turntable, it seems that this step it very important for good results.

Pisa tower .. Markpao? :-)
I use a good carpenter level too with two lines and the bubble not overhanging