Selling on e-bay takes time and preparation and a willingness to possibly loose a little money on fees and to factor a portion of that into your pricing.
First, if you haven't already done so, set up a paypal account that accepts credit card payments. You will pay a larger portion of your money earned to paypal but it's now required that you accept paypal

and accepting a credit card will get you way more buyers. If you don't want people to have access to your e-mail address set up a separate e-bay only account for e-bay and paypal. Also, make sure you turn off spam filtering or you won't get most of your e-bay e-mails (another

).
Next make sure your items are clean and then take nice clear photos of your items. This is best done on sunny days on a plain background. A single colored tile, wood or carpet floor, solid color sheet or bedspread work well. You want to make your item stand out. Take lots of photos from all angles. Upload your photos and crop out any extraneous images (

Seriously, some guy listed his dining set with a lovely photo of his nude self reflected in the mirror in the background

)
Begin to list your item. Find the appropriate category. Unless your item is really expensive it's not worth listing in two categories. Search current listings to see where items most similar to yours are listed. Also check how many items are listed and how much they are selling for.
Describe your item thoroughly in the title - if the item is new or has tags make sure to note that. Use as many keywords as you can without spamming the title. Certain keywords are forbidden. Check e-bay's rules on this.
Be thorough but brief in your descriptions. Describe condition, but don't use negative words unless there is no other choice. If selling adult clothing it's helpful to note the measurement of waist, length, etc. as many people will e-mail asking for this information. If you know little or nothing about something admit it. for example, I bought a lot of pins from for our WDW trip but the kid's decided they didn't want to use them so I resold them, when I resold I noted that I didn't know anything about them because I didn't want to get questions I couldn't answer.
I've found I get a better price if I enhance the listing by changing the font, color of my letters and making the point size larger; I use 18 point or so on average.
Note if you will or will not combine shipping.
Tell people that it's okay to e-mail with questions, and try to answer them all, but don't feel obliged to answer if they ask a question that's rude. If it's a question that will get asked frequently post the answer on the listing or edit the listing to note the answer.
When setting price make sure your starting price is 5 cents cheaper than other listings which start at about the same time - people often look for the lowest start price, bookmark the item and bid on that item without rechecking the price of the competition so undercut your competition from the start.
Make sure to note if you will accept returns and how long people have to pay you. (A week is usually good.)
Determine the weight of your item and have e-bay calculate the postage or calculate the shipping for multiple locations and decide if you'll be better off shipping flat rate box if your item will fit. Add in a handling fee to help off set the listing cost plus the cost of any packing materials, but don't add more than a dollar or two.
I do a lot of buying and selling. I have received lots of recycled boxes and send lots of them myself. Don't feel you need to buy boxes for shipping your items. Also take advantage of the free priority mail boxes from the post office where you can.
Despite what they tell you upgrades to your listing are not really beneficial to your selling price unless you are a power lister or you have an expensive item. But if you have more than 4 photos the option to list multiple pictures and show supersize photos is worth it (this upgrade is only available when you upload your photos - btw ) because it gives you a discount on the photo price.