I use an index card folded evenly along one of the lines on my VPI Classic. Less work and less chance of inadvertently hitting the tonearm with a ruler and possibly damaging the cartridge.
I've heard there are tiny levels out there that can be attached to the headshell or the tonearm tube, but I've yet to see one. They would have to be extremely light not to affect the cart's suspension and thus the VTA. I suppose if such a level could be had, it'd be the most accurate way to set the VTA parallel to the record surface in the absence of such a feature on the tonearm itself (Graham Phantom for example).
Oh, you could rely on your ear and set the VTA to your liking...
I've heard there are tiny levels out there that can be attached to the headshell or the tonearm tube, but I've yet to see one. They would have to be extremely light not to affect the cart's suspension and thus the VTA. I suppose if such a level could be had, it'd be the most accurate way to set the VTA parallel to the record surface in the absence of such a feature on the tonearm itself (Graham Phantom for example).
Oh, you could rely on your ear and set the VTA to your liking...