best way to figure out vta on tonearm

Yes. I guess that is sort of a short answer. Start by Just moveing it up and down. It takes a while and sometimes you may go way to far one way or the other you can always start over. I usually find that if the bass is mushy or muddy it is too low in the back. Move the arm up until the bass starts to focus.Keep going up in very small increments You should find a point where the upper mid and trebel start to become a bit hard or bright sounding. Now back it back down in amounts so small you can hardly see until the trebel smooths out. This should get you to a point where the sound is good top to bottom and with the most relaxed sound and best sound stage. If the maker of the cartridge gives you a starting point like Grado does with the wood body units(they say level or perhaps 2 degrees down in back) use that as a starting point. I Had a Shinon Red that didn't sound good until the arm was so low in the back that the body of the cartridge almost rubbed the record. Other cartridges are just the opposite and you end up with a tone arm set up that looks like a jacked up 68 Nova. I hope this is helpful Jim. That is a cool arm, very well made. I used to like their cartridges in the 70's too.Are they still makeing those?

Before you start playing with raising or lowering the tone arm to adjust VTA, you need a reference point. To start the process, be sure that your tonearm is level with the record surface -- a small bubble level that can rest on top of the tonearm is helpful.

Most of the time, I have found that imaging and focus improve when the rear of the tonearm is just SLIGHTLY lower than the front, i.e., there is a slight downward angle.

As others have noted, getting the right VTA is a matter of trial-and-error, but once you have the level reference point it becomes easier to make changes.

thx. for the above comments: very helpful!
So far with my Grado I've been using it parallel to the record surface with good results but haven't yet tried experimenting much. It did not work very well when tilted upward toward the rear; bass response was lean.
Jvr there is a popular test record available from Audio Advisor.com: it's the Hi Fi News & Record Review LP (a.k.a. HFNRR). I just received mine but haven't tried it yet. There are a number of different test tracks for optimizing VTA, tracking force, antiskating force, etc.