In addition to the essential advice already given, I would like to add that if you want the best end price, start your auction at no more than $1, and if you REALLY want a good price, do not use a reserve! [Note that this only works on items with some demand--you don't want to get stuck selling an item worth $100 to one lone bidder who bid $1. To check demand, check completed items for the specific item you are selling]
Next, the time of day and day of week have a lot of bearing. Try to end your auction at a time when many people will be bidding, such as between 4-10 pm Eastern time (you get some of the work people on the west coast and the people at home before bed time on the east coast). Also, ending auctions on the weekends is good, especially Saturday morning or afternoon, and Sunday afternoon or evening.
If you have an item in great demand, use a Buy It Now price that is reasonable, but a little high. You might just get it. If you want a quick sale, make the Buy It Now less than others selling the same items, and less than the completed items price of the same items. A gallery photo is a must. Good feedback is a must.
There are three kinds of ebayers:
1) Honest to a fault, completely committed to the other party's satisfaction. Will pay within minutes or at most hours of auctions end, and if selling, will ship within 24 hours of being paid. Will overpad to protect items being sold. Will answer all emails within one day and will ask all pertinent questions immediately. This is the best kind of ebayer. This is the type of ebayer that I am (user ID: spinne1).
2) Generally honest in that you will get your item and it will generally be as described. Seller may be in no hurry to mail it to you. You may get your item in two-three weeks. The item may have some undisclosed fault that you can live with. Email is often late in coming, but usually does eventually. Often, this seller is either: new and does not understand what is expected, or a "power seller" business dealing in liquidating piles of stuff. These sellers often don't have a good idea of the exact condition of the products they are selling and may not back up their products when there are problems. Emails often go unanswered. I AVOID THESE SELLERS LIKE THE PLAGUE AND YOU SHOULD TOO. To spot them, look at the total number of negative feedbacks. If it is more than two, be suspicious. If it is in the hundreds, run away!!!!
Buyers in the second group delay in paying, or act like they are not obligated to buy. They may ask questions implying that they will buy IF conditions are met.
3) Outright crooks, they use ebay for fraudulent purposes and never intend to deliver any products or cash. Sadly, there are too many of these folks on ebay now. It takes a savvy user to spot many of them. Some dead giveaways are tons of negative feedbacks, big font email addresses in the description that you are asked to use to complete the transaction, and requests to only use Western Union to send the money. Another red flag is a price that is way too low, as in a Buy It Now price.
Being the first type of ebayer will help your items get much more interest. I can't tell you the number of items I have passed on just because I could tell the seller was in category two instead of one.