Keep your chlorine level between 3 and 6 at all times until you have some CYA registering in the water. The link to the CYA/chlorine chart (aka "best guess table") is in my sig.

Once the CYA is in the water, you don't need to test for it more than monthly or so, unless you're using stabilized products in the pool. Once the CYA is there, the only way it's going to decrease is through splashout or frequent backwashes.

Janet