It's important to note that you always have LH in your system so you will pretty much always see a second line all month long. For me my lines stayed fairly faint most of my cycle, sometimes getting darker and sometimes getting lighter until they were clearly positive (test line is as dark or darker than control line).
Some people have their lines get darker as they near ovulation, some don't. You really can't judge where you are in your cycle by the darkness of the test line. Just test until you get a clear positive.
As for when to test- don't test in the morning as your body produces more LH later on in the day. I always tested when I got home from work around 6pm. Just don't try to drink too much water before hand. I always had 2 days of positive tests while other women might only have one.