One of the most important lessons I've learned to help sell items on eBay is how to price them so they will sell.
There are three factors sellers must look at when pricing an item: 1) what is the lowest amount you will accept for your item, 2) what your product is really worth (are we looking at a true Picasso or a reprint?), and 3) what kind of time do you want to move your product in?
eBay has some really cool tools at our fingertips to use to help us price our items. We can click on the Buy box at the top of our page which will take us to the eBay home page where we can do a search for the product we are looking to compare. Once you pull that product up, you can see how many of that item is currently being sold on eBay. Is now the right time to sell? What are the starting prices. What are the current bids? Write down all this information. 
Another tool to look at is in the left hand column  -- there is an item with a box called Completed Item List. If you click the box and then scroll up and click the search box, a list will come up that will show you how many of that item has sold recently and what it has sold for (and how many have not sold). The thing I like best is that you can go to the sold item's description and still see what the starting price was -- which is extremely helpful when trying to determine a starting price for some of my items.
Okay, so now we have an idea of what our starting price is. But we know that our item is worth a lot more than that. What do we do? Easy - use the Reserve Price feature. The Reserve Price is an amount you set that bidders have to reach or you are not obligated to sell your item. The neat thing about this is, if you have a bidder that almost reaches your reserve, you can offer them a Second Chance Offer to buy the item at their bid -- and bidders will often accept your offer. By setting a Reserve Price, you can set a very low starting price and still try to get your asking price without the fear of having to sell too low.
When you list your item, you should know how long you want your item to be on auction. You can have it on for 10, 7, 5, 3 or 1 day. One day is usually for more "at hand" items like sporting events, shows, airplane tickets and the like. Most auctions run 5 or 7 days. However, if you have a great item like a car or a motor home, a 10-day auction is probably the best bet so you can try to get as many people to view it as possible.
One thing that I have observed: a 7-day auction started on a weekend day that runs through the week (so it runs through a Thursday and ends on a weekend day) is probably going to get your item noticed by the most prospective buyers. Don't ask me why -- I have just observed that if you start an item on a weekday and end it on a weekday, it doesn't do as well.
Well, I hope these little tips have helped. The best way to learn how to sell on eBay is by doing it and by using the tools and learning materials eBay offers. eBay has some great things here to help you succeed. Just use them! Good Luck!