Knowing the condition of your comic book will help in knowing the value of it. Grading your comic allows you to describe the condition that it is in, and there is a universal scale which is used. Grading your own comic is subjective. The Comics Guaranty Company, or CGC, can grade your comic for a fee. Doing this will provide a third party opinion and make the grade less subjective. They use the same scale as well so it's not always necessary to pay them to do the grading for you.
The highest grade a comic can receive is "mint". If a comic is in mint condition it should look like it just came off the press. For a comic to be in mint condition there can't be any tears, cuts or creases. The comic should be able to lay flat on a surface without any rolling or curving of the pages. The spine has to be the same way, completely straight. The staples in the spine have to look new and can't have any rusting or unusual bending. The pages of a mint condition comic can't have any fading or discoloration, marks or smudges, and there can't be any rips or tears. The only accepted marking on the comic allowed is an autograph.
Not every comic can be perfect, and the next best grade it can receive is "near mint". Older comics that are in near perfect condition usually receive this grade. Overall the comic should look like new, but there are a few exceptions allowed for this grade. If the cover is slightly off center it will be considered near mint. Other conditions that will give your comic a near mint grade are minor bindery tears and minor fading of the pages. All other aspects of the comic will have to be perfect.
If a comic has minor imperfections the grade usually given is "very fine". Over time and use of the comic, it can be worn or damaged. However, to be graded very fine the comic can only have minor problems such as wear around the staples in the binding or a small crease on the cover. The color on the cover and pages can be slightly faded as well.
For comic book collections that are used and read, not just collected, the grade is usually "fine". Because the comic has been open and read there are usually creases on the spine and pages. The staples can have some discoloration or show signs of unusual bending. Minor stains or tears to the pages will result in a comic being graded as fine. Fine graded comic books are above average in appearance.
The average comic book that has been read is graded as "very good". A well read comic will have stress to the staples in the spine and obvious creases. The comic has to have all of the pages still intact as well. The cover and pages are allowed to have discoloration and fading, but there can't be major tears. A small tear is allowed for this grade.
As comic book collections start to lose value, and you can tell that they have been used and well read the grade given is either "good" or "fair". The issue is worn down, has major defects, but it still readable. A good or fair grade will be given if the cover has been detached, has tears and creases along the cover and pages, the pages are marked or stained, and the spine is in bad condition. If pages are missing and the cover is gone the comic will be graded as poor.
What other types of vintage collections are you interested in? Do you have one? If so, share some of your best with us.