There are several ways to sell items on line. Each has its own advantages and disadvantages. First there is Ebay. With ebay, your items are seen by more people which may mean more money. We like more money. The downside is shipping and the small fee ebay charges. The other option is craigslist. The advantage is no shipping, but the downside is smaller market. I have used both. Currently I like craigslist better, because I do not have to ship and it is free.
The other option I use is local just for me. It is a facebook page someone set up called Flowood Yardsale. It works very much like craigslist....no fee, post a pic and description, meet the buyer at a public location. It has been very successful for me. I think people like knowing who they are buying from. This facebook page is really only good in my local area, but anyone could create their own facebook page or at least check around to see if one already exists. Good luck!!
By the way, I made $16.50 today. I picked $6.50 at a consignment store and sold a shirt of my husbands for $10. I call that a good day!