Once you do what Earthling said (dump juice, clean tank, change coil), then let sit for at least a couple of minutes (five is playing it very safe), to let your wick absorb juice sufficiently.
Then, you start at the lowest setting. Vape. Not to your liking? Turn it up a LITTLE. Vape. Repeat until you get a slight burnt taste or a little bit of a harsher vape than you like, then back it down a notch.