Something that I just noticed today. If you are testing fairly early, like 10dpo, and pee into a cup, you should leave the pee sitting for awhile. It will mean the difference between a very faint line and a darker line. I just got a two-pack of a test, and the first test, I got a super-faint line. I left the pee sitting for about an hour, and took the other test, and it was a much stronger line. First morning urine doesn't work that great for me, I drink a lot overnight, so that's an alternate thing to do. I guess it's kind of obvious.