Depends on the situation, normally I light everything by eye, I ask myself what is the mood, the intension of the scene, I think In how lighting can ruin or help the scene, how do I think it will look correct how do I want it to look.
Than if its important I choose an Fstop for they key light and go on from there by eye and if its necesary I check the ratios with the lightmeter at the end.
I think is more important to focus on what the light has to say and later you can meter and adjust ratos.