The first step, check when sunset is tonight! You can find this on most weather forecasts or just Google the words 'when is sunset' and Google will work it's magic. It's best to be on the lookout in the afternoon for high or mid level clouds, or if there is a big storm passing through in the afternoon, these are good signs that you could be on for a dramatic sunset. If you're going for it, head out to your planned location about an hour before sunset. This will give you plenty of time to get out to your location, and scout about for the best angle. My biggest tip to do with time however would actually be after sunset. Don't leave as soon the moment the sun drops below the horizon. Stick around, often you'll find the sky lights up 10-20 minutes after the sun actually disappears.