Welcome to AA!
It sounds like you are cycling your tank right now, good job! If you aren't, read the cycling stickies on the Getting Started section, they will help a lot!!
Anyways, you should really change at least 25% of the water one to two times a week depending on the stock.
When I do water changes on my tank, (it's 25 gallons) I take the old water out with a bowl, and poor it into 5 gal
buckets until I get however much I am changing out that day, then poor it into out sump.
The I go upstairs and get tap water and just guess and try and get it as close to the temp in the tank as I can. Then bring it downstairs, put it in the tank, and put some declor in it.
When I am doing a water change I have the heater and filter off.