Vinyl records grading scale


I am sort of new to vinyl and am building up my LP collection. A very prime source for it is the internet used market where appears to be sort of a grading scale system to rate condition of vinyl records on sale (G+-, VG+-, EXC, NM, etc). Is there any place I can refer to for the criteria or guidelines as to what to expect from the different ratings?
Also, what has been your experience buying used, and what is the lowest acceptable rating to get substantially noise free (tic/pops) records? Please let me know, thanks.
jmr
From the following grading
Mint, NM, Ex, VG+, VG, Good, Fair, Poor, and Trash

If you have an expensive cartridge (over $300), which would be the least condition that you will be trying with your cartridge? How about for budget level (under $70)?

I have over 500 LPs, and most of them (about 300 that I bought from Garage sale at under $1.00) are Good ~ Trash condition. So far, I have not bothered play them on my Grado Black cartridges and inexpensive Shure cartridges. I recently purchased more expensive ones, and I wonder whether I'd rather be more careful.
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.
I agree that you need to get to know the seller. If you don't know the seller, you should assume overgrading. Even though VG is supposed to mean "very good," it actually means "vertible garbage" in many cases, especially if you only like to listen to dead quiet vinyl. One time I ordered some records from a large used record store that sends out a regular email list. Some of the records were listed as VG++, but the covers looked like a dog had chewed them and the records inside didn't look much better.

If you are spending the time and money to clean with a Loricraft (or any other record cleaner), I wouldn't bother with anything less than NM- or EX, unless you know the seller really well, or it is so dirt cheap, it is worth a try.

Good luck.

Mark
I dislike adding the "EX" grade in between VG+ and NM, or the use of "++" or "-" anywhere. Too much BS wiggle room. Folks should just stick with NM, VG+ (or EX, take your pick but not both), VG and G. Everything else is just the symptom of creeping grade inflation -- when you no longer define VG as actually being "very good" but "fair" instead, you run out of enough gradations at the top and start needing to add more. The solution is to grade properly to the real definition, i.e., VG should literally mean "very good" and G should mean "good", not "awful". This is the same nonsensical situation Stereophile has boxed themselves into by allowing a grade of B to become the lowest possible grade a component that's not inexpensive can earn without it being seen as a total failure, and assigning a grade of A to 80% of what they review. Therefore they've added a new grade of A+, and sometime they'll have to start adding A++. Meanwhile none of the grades any longer mean what the definition key they ridiculously keep on publishing says they're supposed to mean.