How can I tell what version of an LP is best ?

Find a good local record store. I am lucky to have a few in the Seattle area. It is more fun to thumb through the "bargain bins" thansearch for the best pressings of X.

Generally the original one is the best (higher frequencies, tonal colors), of course, there will be always some exceptions but I never had a top Reissue from a inferior Original. When you have a very good Reissue, then the Original Master or Copy is also excellent. A lot of knowledge died when the Plants closed, based on that, lots of reissues are noisy, or can be silent, but then they can sound dead and boring in comparison to an Original. And indeed, sometimes CD's aren't that bad...

No worries, Saki...none of the genuine respondents thought you were dissing CD at all. :^)

Neither was I BTW.... I will repeat the statement that selling a perfectly serviceable record library on the strength of powerful advertising and replacing it at great personal cost was madness and still is.
My admiration goes out to all those who proved refractory to highly persuasive marketing and social prejudice. ;^)

As to online shopping, nothing wrong with that either. They generally describe the product quite well but this can be misleading on occasions. I've bought a few by this method but most are acquired by trawling the Charity shops which have really become Modern Record Shops. Their staff are becoming very organised and discerning at grading vinyl as they see this as a rich seam of revenue now.
I'm delighted to support those charities in this way.

On the rare occasions I reject something it gets recycled back to the Charity Shops for free.(I only hope I don't re-purchase it! :D )

Just wanted to report back...
I took the suggestions and went to the links as well as subsequent ones listed there . They did do exactly what I was looking for . They listed the best , and often 2nd and 3rd best , copies of popular LP's . They also went so far as to list the bad copies !
Unfortunatly , I am not the only one seeking this info ! Trying to locate one of these primo copies is quite difficult if not impossible . And when one is available , it can be priced into the stratosphere !
So I guess the best deal is to just try to find a disk that is in as good of shape as possible .

Thank you for all of your help .

Or you can ask Tom Port. He rates the Lp's and sells them ---> Hot Stamper