Well you need a camera, a decent camera that can take reasonable pictures if required. Note that the images do not have to be hi-res or extremely large prints. They will be viewed at 72dpi (that's the resolution of the monitor) so you can get away with an image no smaller than 500 x 500 pixels. Do not do what most people do and set the camera on the highest setting, you're only wasting valuable time when manipulating your images.
Next you need a tripod or camera support of some kind. Ask any reasonable photographer how the quality of their images increased when they started using a tripod. The results speak for themselves. You also need some Imaging software, not necessarily Photoshop, but you may need to resize and tweak the images. You should have something on your PC already. It's worth playing about with the software and learning the basics. It'll pay dividends later.
Moving briskly on the next item on your shopping list is a background. Like most experienced eBayers I prefer to use a white background and isolate the item. I feel it makes the item stand out and looks more professional. For this I simply use a white sheet of card. If you're shooting a lot of items and some fairly large then it would pay to invest in a sheet of white faced hardboard from the local timber merchants. This being easy to wipe over and keep clean.
That brings me to lighting. Soft lighting and the softer the better. Good quality soft lighting does not create any hot spots burning out any details.
You can go out and buy a studio flash and a light tent, which is fine if you can afford it. However, I always used to use natural light. Natural light created by a cloudy sky. But you can pick up a light tent pretty cheaply on eBay and I would recommend that you invest in one. One other thing to remember is that if you are shooting in a light tent them you need not buy a background! Forget the lights though, at least for the time being.
So to work … Clean the item thoroughly. I always use cotton gloves when I am handling items. Place the light tent outside on a table or other surface. Carefully place the item centrally in the light tent and position your camera. Take a few shots at different exposure settings notifying the settings used. You will find this information very handy when photography items I the future.
Transfer the images onto your PC and take a look at them on the screen. With you editing software resize the images to 500 x 500 pixels and view them at 72dpi. Increase the brightness by around 20. This should give a detailed image on a clean white background. If there are any marks on the white background you can remove then with the software. If the item has lost any detail play around with the brightness and contrast levels until you are happy with the final image.
When you are happy with the results – save the image into a selected file on your computer. You are then ready to upload the image to the auction site.