I have to say that this is probably my biggest issue and through all that I've read I have a plan. I'm going to purchase a low, medium, and high and also some 0 mg ejuice. I plan to start with the low just to test out the ecig. I already have a feeling that I will need the medium, who knows, I might need the high. However, I would rather start out trying the low and saying "No, this isn't doing for me" and then go to the medium. Possibly the medium might be more than I need so I mix the low with the medium and try that. I would rather start out small and work my way upward then OD and end up going through some of what I've read here.
Put it this way, it's probably like being a mad scientist in the beginning! It will be trial and error but I would rather err on the side of caution.