Assess the textbook's condition. Is it in excellent condition? This means that the textbook could pass for just about brand new. Is the textbook in good condition? Good condition is when all of the pages of the textbook are accounted for, but the binding may be a little loose, or there may be a few marks in the book. Is the textbook in fair condition? Fair condition is when the textbook may be missing some pages or contain writing throughout the book. Finally, there is a category for poor condition. If your textbook is in poor condition, you might as well scrap it, because no one will buy it.
Get a digital camera and take a picture of the textbook. Buyers want to visually see what they are getting before they buy it. Digital cameras allow you to upload the pictures to your computer.
Choose whether you want to list your textbook on eBay or Amazon. Amazon will leave your listing on for a long time, while eBay is designed to sell your book within a week. Amazon doesn't charge you a fee, however, where eBay does. You can also try eBay first and then resort to Amazon if eBay doesn't work.
Join a homeschooling forum. These homeschooling forums have sections devoted to selling textbooks to other parents on the forum. You can search for homeschooling forums by typing "homeschooling forum" into your search engine. Browse the forums until you find one that has a section for selling the textbooks. Register and post your textbook for sale.
Join a homeschooling group. Yahoo has a lot of groups, and the homeschooling groups allow you to post your textbooks for sale. Then other homeschooling parents who need that grade level can buy the textbook, or they can make you an offer. You can accept the lower offer or keep trying to sell the books for the price you want.
Take your textbooks to a homeschool convention. Many homeschool conventions have tables of used homeschool textbooks for sale. This option is only a good one if you have a lot of textbooks to sell.