I'm nowhere near professional with my photos, but I've found that these helped to improve the ones I took quite a bit:
* Have nice and bright lighting. Flash is hit or miss and can wash out the subject so I don't use it. But overall bright ambient lighting helps the camera focus better.
* Use contrasting background. I use dark beddings for my lighter colored hams, and white bedding for my agoutis. This will help having the hamster stand out.
* Take lots and lots of photos. I usually pick the best 2 or 3 out of a set of 50+ photos taken in a sitting. A lot of them are blurry, but it's good to have lots of options.
* Do light touch-ups on the computer if you can. I like to do small amount of color correction as my room lighting (don't have professional light sets) makes a yellowish cast over all my photos.