There are a couple of routes you can go. Here are a few:
1. Grade them yourself via assistance from the book OVERSTREET'S COMIC BOOK PRICE GUIDE.
2. Have someone who is knowledgable about comic books, preferably a friend, help you.
3. Take your comic books to a comic book store and ask for someone to help you. (please read my added info about this)
4. Look for comic book buyers in magazines such as Comics Buyers' Guide, Wizard, etc. There are collectors and companies that advertise in comic related trade publications.
5. If you have money to spare, there is a company called Comics Guaranty Corporation, and you send in an issue, they grade it for you, put it in a protective plastic case sleeve with all grading info. While this is a "professional" way to have your comics graded, it will cost you. It's not cheap.
My first recommendation on this list is what I encourage you to do. There isn't any reason an individual can't grade on their own. If you can obtain this book, OVERSTREET COMICS BUYERS PRICE GUIDE, which is usually available at libraries, Waldenbooks. and other book sellers, the preface to the book has specific information on how not only to grade, but the definiton of collecting terms, how to collect, how to buy and how to sell.
It is also helpful if you can find a person who is a collector, and not an employee at a comic book shop or other business. The odds are they will be very glad to help you grade.
There are things to bear in mind about your comic books, and they are condition, age, and "key" story issues.
Comics from the 50's are generally considered "Golden Age" and are harder to find, especially in Very Good to Very Fine condition. Comics from the 60's are considered "Silver Age", and while a bit more common, these are still hard to find as most collectors don't let them go. The comics from the 70's to early 80's are considered "Bronze Age", and most comics after approximately 1982 are considered "Modern Age".
I don't recommend taking your comic books to a comic book store. Why? There are very few people at these locations who would be honest with grading your comics properly and truthfully. It is sad, but it will be more than likely they will grade them lower than what they are worth, offer you a low amount, and then buy and later sell them elsewhere at your expense.
The book I mentioned, OVERSTREET COMICS BUYERS GUIDE, is published every year, and you may find books from 2, 5, 10 years ago.
Just get a copy, no matter the age, and read the info inside about collecting, grading, etc. While prices may fluctuate, try to get a copy that isn't more than 5 years old.
Lastly, I am a private collector, and you can contact me, and I will be happy to assist you in any way. I am not trying to buy your comics, I actually enjoy giving assistance with this hobby.
You can go to Ebay, but you have to set up a few things, such as info, pictures, etc. If you go to a comic book store, they may buy your comics immediately, but at a fraction of what they are truly worth. I do suggest Ebay, and a lot of us who are serious collectors, often use this, but there are few good comics being offered lately. Ebay is better if you have time.
I hope this helped.