When I have the idea for a video I go to the youtube search bar and start typing in a keyword that is associated with my idea...for expl...say i want to make a video on ranking a video...I will type ranking a video on the search bar.
Next I will go through all the youtube suggested phrases that relates to the video I want to create and look at the competitions on the various phrases.
When I find one that I think I can rank on it... I use it as my video Title