Here are some basics for those who are
not goldfish pros, this may seem common sense, just starting out
is hard and use this as a guide which would hopefully help you
from time to time.
1. Keep it in water, OF COURSE!!!
2. Always love your fish.
3. Feed you fish at least once daily, with goldfish flakes, food, or with brine shrimp.
4. If the water becomes murky and is turning greenish, go ahead and clean the water NOW!! Please remember to take you fish out first. If you are using soap, make sure you rinse out your fishbowl/tank/aquarium out thoroughly. Some traces of soap residue might be poisonous to fish and might even kill them! Or simply, use water and a sponge to wash your tank.
5. Make sure there is an ample supply of air. If you have an air pump/purifier go ahead and use it. It doesn't have to be "on" all the time. If you don't have one, it can found at your local pet stores for $4.99 and up.
6. ADVICE: If you are an owner who leaves your tank light on 247 (24 hours a day, 7 days a week), try to learn not to! Fish sleep when you sleep, even though they don't have eyelids. So advice is, to leave your light off, only use when necessary.