Vinyl records grading scale

Guys, thanks very much for your quick responses. John/Arahl thanks for the links to the grading scale. That is exactly what I was hoping to find so that I can have an Idea of what each grade should represent.
I am very aware of the necesarily subjective nature of this process and the fact that most gradings will be a bit overstated. I am sure I will develope a feel for them after a few purchases I just want to narrow down the learning curve in terms not getting to many really bad ones.
My main concern is really noise when playing them more than visual marks wich in many ocassions do not affect playback.
Yeah, I put on my analog rig a Loricraft since inception which I consider mandatory some kind of decent RCM.
Any other comments with respect to cutt-off point for records from your experiences; or any other savy advices?
Thanks...

I guess that based on responses one would ideally stay on EX/VG++ or above unless there is something really special that you want and theprice is adequate.
My limited experience has been that you can aproximate the noise level of most records by visual grade on relatively clean records. I suspect most of the ratings you see on sale offers are made pretty much that way. Again, thanks for your comments.

In your experiences where are the better source of good sellers? Ebay? Agon? other forums? private sellers or dealers? Thanks.