Before you start using adjustable Voltage/Wattage, I highly recommend you understand Ohm's Law so you don't blow a battery up in your face and die.
Just read this and follow the chart.
http://ecigarettereviewed.com/ohms-l...ned-for-vaping
Basically, whatever coil you are using, you should know it's resistance. Most coils are around 2 Ohms, which means 3.7 Volts is your sweet spot. Most coils have their resistance printed onto them like the one below the chart.
