1. Check your camera's white balance setting, and set it to incandescent or flourescent light (it's a lightbulb icon on my camera) for indoor pictures to get truer colors. (Note the yellow cast on the picture of Ben's Halloween candy. It's so much better in the ones in my mosaic below!)
2. Without flash, photos taken in low light can have a lot of noise or easily be blurred. Changing them to sepia can sharpen and provide much better detail. (Note the two versions of Ben and the presents in the mosaic. This photo is quite fuzzy full-size--the color is nice, but the sepia version looks much clearer.)
3. Pictures with lower resolution often look great if they are smaller. You may not want to print them, but they can look great on your blog or in a small slot in a photo book.
4. Susan's pictures were action shots, so she increased the shutter speed (a.k.a. sensitivity or ISO) to keep them from being too blurry. This results in lower resolution yet, she pointed out, which is why she kept them small and used sepia. (Edited: Actually, for Susan's accurate explanation of this, check the comments! I lost some info in my translation--which incidentally happens all too often in my photography as well. ;-) )
5. She also recommended that if possible, move the subject close to a window or lighter area.
If you can use these tips, then go try them out, thank Susan, and pay them forward!