The way I have mine set up for night is the two dimmest ones are on flash, the main one is the brightest and that one is on steady mode, during the day (depending on where I'm riding if I even have it on) I only turn on the main one and put it on flash.

I'm not saying my way is the best way, it's just what I do because I read two different studies on flash vs steady, European studies show that steady is the best and it's not even legal to use a flashing light there; however I read a Canadian and US study that showed that flashing is better; so I decided to cover both spectrums! I have no idea if what I do works, I know I've never been hit from behind but then again I was never hit behind before they even had tail lights, so I don't know, I just do it.