Without a photo you can sell a ' 12" HEAVY DUTY HACKSAW + 1 BLADE - BNIB ' but you stand a slim chance to sell a necktie.
Sometimes the photo is useful to convince the buyer about you: if you sell a Mac Mini and you have little feedback the photo shows that at least you got near one - do not just pull a photo from a web site. In the rest of the cases the photo had better be good. So what does it take to make a good photo?
First - look at what you have done with a fresh eye... if the portrait you shot looks like a lamppost growing out of your lady's head then it is not a good portrait. Shoot another one.
Same for items to sell. Buyers want to see the item and see it well. No use to show them the bedspread the necktie is on. But it is useful to see the texture of the silk (not everyone understands technical terms and they still want to wear ties. On top of it most of them think they have an excellent taste).
It is useless to photograph a bike from the left and from the right but it is useful to show on a second photo the type of the brakes from the front (with the state of the tyres while you're at it). If you mention a default of the item it is better to show it (or buyers will imagine worse).
Second - light. In low light
Most digital cameras try to compensate automatically for the kind of light (incandescent, sunshine) but as they cannot see the whole room they do it wrong. If you take a small object on a yellow background the camera thinks it is the light and will shift all the colours towards the blue to compensate. This is one more reason to have the object fill the image. Same thing with brightness: a small black object on a big white background will become a black spot without details.
If the colour balance is still wrong, put a sheet of white paper behind the object - that will give an idea of the real colours and eventually of the size.
With the sunshine the problem can be that one side of the object is well lit but the other is dark - a reflector (ex. tinfoil) on the other side can work wonders. Ask someone to hold it, it does not have to be stable. For jewellery use several light sources.
Avoid taking photos while you are facing the sun - if it is a house (orientation being important here) wait for the afternoon. Photograph a flat object with the sun behind you (avoid having your shadow on it), with the sun on the side (light tangent to the surface) if you want to show the texture like of REAL leather and inbetween if the object is not flat and you want to show the shape. With a digital camera you can take several pictures and choose later.
Way down the list - your camera. Go to the sunshine before blaming it. If you still want to sell it, put it before a mirror and use the self timer.
If you can look at any object, scene or person and see what it will look like on the photo then you have become a photographer.
Now - you have a digital image. The eBay site reduces the images to a size of 400 pixels (- different sizes recently) in height and in width. So take a graphics program and cut out a part of your image filled by your item. If it is bigger than 400 * 400 pixels, reduce the image size yourself with the graphics program.
The eBay site reduces the size of the images by subsampling (throwing away rows and columns of pixels) which will turn the fine purple checks to thick stripes of moire - the finer the checks, the wider the stripes. Your graphics program can reduce the image by averaging colours of neighbouring pixels with much better results.
To show the checks of the shirt paste a piece of another photo in a corner of the first one (separated by a black or white frame) - this is still priced as one photo.
That's all folks.