I tried to sell something on eBay but was an idiot and had to take it down. I didn't realize that the bidding increments were so small--I had imagined they would be $20 or so (I had a starting bid of $150). But they were only $2.50! So I had way underpriced myself for the opening bid, which I had lowballed assuming that the subsequent bids would take me where I wanted. I had to take the item off after the auction has started, which you can do if there is less than 12 hours left. But you're allowed to do that only once per calendar year without penalty.
There's a lot of info on the eBay website, but it can really drive you crazy trying to learn everything. I think you just kind of learn what you can and get started and learn as you go. I did find that their phone customer service was quite good and answered my questions. Calling was a lot easier than digging through the website.