The numbering system everyone uses confuses me.
My selling background on Ebay consists of selling vintage paperbacks. For paperbacks I use Very Fine, Fine, Very Good, etc. I never ever grade anything Mint. Mint is a candy, not a grading description. Occasionally I sell Magazines and records. With magazines I can use my paperback grading description. Not with records though. With Records I use the Goldmine Grading Standards:
http://www.eskimo.com/~bpentium/beatles/grading.html
As people have mentioned above pointing out the defects in your description can be very useful to the buyer. A 6 with a bent corner to a buyer might be much worse than a 6 with cover rubbing. Just depends on the buyer.
I will attempt to convert a number to Goldmine. Correct me if I am off on this.
A 6 cover is Very Good+. A 6 disc is Very Good+.
A 7 disc is About Fine. This is where Goldmine differs from other grading standards. They do not allow you to call a record mint if it is sealed in the sleeve. Because records were inserted by hand they could have scuffs. I myself have opened factory sealed discs only to find a scratch or fingerprint. And what about glue at the edge. Anyone grade that?
A 7 cover is About Fine. No splits. Tiny crease. Minor rubbing. If it had a tiny crease AND rubbing it would get knocked down to VG+.
A 8 cover is Fine. Same with disc.
A 9 is Very Fine. No flaws anywhere.
A 10 is Near Mint? As new as the day it was published with no flaws at all. That includes manufacturing flaws.

Hmm

I see it more like this :

10 - New/sealed/perfect
09 - New/sealed/with some minor flaws (hole in wrap, crack on spine)
08 - Used/perfect/mostly still in wrap
07 - Used/with some minor flaws
06 - Used/with flaws (bent corner, pushed in corner, etc.)

I like this approach - very clear and easy to follow.

takou has the pulse of it.
Once again I find myself agreeing with laserdisc_fan on this.
Very clear and easy to follow !
The scale tutorial is easy to use when in doubt !
Thanks everyone !