I take my pics at night. There are 4 windows in the fish room so good daytime shots are almost non-existant. If you don't have a tripod, then do what I do, a stack of various sized phone books on a stool. Add or remove different phonebooks so your camera is at the right heigth for what you are shooting.
I take shots with a flash, and some without. Sometimes both to see which comes out the best.
Jchillin hit it just right. Good advice.
There are many other settings on your camera, but just stick with taking sharp/in focus pictures first. I've only had my digital camera for a year now and I am still learning how to use it properly.