The key is to cheack the control box which every pregnancy test kit has, to ensure if its working properly.And please dont get confused here with a positive result. You should also be certain about where the control line should be. If you cannot see the control line, the kit is of no use, throw it away and look for another one,because this meansthat the test is not working properly and will not give you an accurate result. Always check the expiration date on the box. If it is expired throw it away and get a new test.

The best time is to check with the first morning urine.\, because at this time the urine is the most  concentrated and would have the highest levels of hCG. Over the counter pregnancy tests will say that you don't have to wait for the first morning urine to get a result, but if you want to be absolutely sure, testing the first morning urine is a good idea. The hCG could be diluted at other times during the day, especially if you drink a lot of water or other liquids.