General Tips...

See also "Ideal Fish Section".

My opinion on fish bowls(and the beta-in-a-vase-with-a-plant-things)
Anyone who has ever written to me regarding a sick fish kept in a 1 gallon tank will probably have heard my rant about fish bowls. I am very much against keeping fish in fish bowls. Fish bowls require constant cleaning, and the methods people use of "tipping the bowl" to clean them will stress the fish. Also, pH and ammonia levels cannot be properly monitored, and neither can temperature & oxygen. Your a lot better off keeping your fish in a real tank, even a small 10 gallon will do and they are relatively inexpensive (like $10, I've seen them). With a larger tank, you can add filters, airrators, and have an all around better environment for your fish to live in.

Removing sick fish from tank
This is risky business, because sometimes removing a sick fish is a bad idea. In my opinion, the only time it's a good idea to remove a sick fish is if it's suffering from a fatal illness (I place any illness that is not treatable by simple store bought medication in this category.) If the fish has an ailment such as ich, or any other ailment that can be easily treated, then it's a good idea to leave the fish in the tank and treat the entire tank for the illness.

General Info

Always keep an eye on new additions to your tank. Disease tends to come in with new fish.

Never use soap when cleaning out anything that is to be in the aquarium. I think rinsing with hot water is a good idea to help clean things off.