Here is my guide on how I grade cards. I use these grades to help describe all pre-1980 cards in my for sale listing. You will see I sometimes use ranges for card groupings as well (like EX-NM, which means all cards in that grouping are at least EX with some being better). I usally use groupings on less expensive cards where the difference in price between major grades is minimal.

M (Mint)

Card is perfect out of pack condition. All modern (1990 and newer) cards are assumed to be in this condition unless noted. Rarely do I use this condition for pre-1990 cards.

NM/M (Near Mint/Mint)

Card is almost perfect out of pack condition. I use this condition for pre-1990 cards that most people would call Mint. I just don't like calling older cards Mint.

NM (Near Mint)

Card is near perfect specimen. Great color and focus, decent centering (60/40 or better), no defects of any kind. A very nice card. This is usually the highest grade I give to pre-1990 cards, mainly due to printer quality control.

EX/NM (Excellent/Near Mint)

Card is a strong EX but not quite NM. I use this grade on slightly more expensive cards to give a break between major grades.

EX (Excellent)

Card is a very nice specimen. Good color and focus, centering may be slightly worse (70/30 or better), no major defects of any kind, card may have slightly softened corner(s) but still very square. Still a very decent card. This is usually the most common grade of 1960's-1970's cards. I may also put a higher grade card in this category if it is really nice but has some prominent defect (like being off center or having a slight crease).

VG/EX (Very Good/Excellent)

Card is a strong VG but not quite EX. I use this grade on slightly more expensive cards to give a break between major grades.

VG (Very Good)

Card is a little rough but still a very displayable specimen. Color and focus may be off, centering may be way off (miscut), may have one or more major defects, card usually has fairly rounded corner(s). I still list any major defects for this grade in parenthesis.

G/VG (Good/Very Good)

Card is a strong G but not quite VG. I use this grade on slightly more expensive cards to give a break between major grades.

G (Good)

Card is pretty rough and is usually only good for a filler or type card. Color and focus and centering may be way off, usually has multiple major defects, card usually has very rounded corner(s) or damage of some kind. I usually don't list any defects for this grade (just expect it to be pretty rough).

Poor

Card is extremely rough and is only good for a filler or type card. Always heavily damaged. I usually only sell cards in this grade if the card would have been very expensive had it been in better condition.