OPK’s

Does anyone have any advice on OPK’s .. like what time of day is best to do it? When to start in relation to af? How to get into a routine of it? .. i tried once and after 2 weeks i decided it was too much, i was always forgetting to do it and didnt really know if I was doing it correctly. After trying legit EVERYTHING I decided I should try again but I want to make sure I am doing correctly this time. Thanks ladies :)