Before you start vaping initially, or if you have just changed your coil or clearomizer/tank, whether it’s classic vaping or Sub-Ohming, always remember to prime your coil.
For classic e-cigarettes, all you need to do is fill up the tank as you would, and assemble the rest of the device. Then allow the device to stand with the tank filled, fully assembled for 5-10 minutes. This standing time will allow the e-liquid to fully saturate the coil, so there is no risk of dry-burning the coil out when you start vaping. To speed up the process a bit, you can also simply draw on the clearomizer without powering up the battery, to help drag the e-liquid through the coil while inhaling/exhaling. Please bear in mind that you should use a steady draw because sharp hard draws could flood the clearomizer.
With Sub-Ohm devices, there are a few different ways to prime a coil depending on which type of atomizer you are using. If you’re a beginner and just starting off with your first Sub-Ohm device, it’s the same technique as priming the coil with standard e-cigarettes. Simply fill up the tank and allow the device to stand for 5-10 minutes to allow the coil to become fully saturated before you start using it. You can also drip the e-liquid directly onto the coil to speed up the process slightly — avoid over saturating the coil itself as it can cause a bit of spitting of the e-liquid for the first few draws. Of course, some vapers like a hot vape so they enjoy this experience! Experiment and find out what you prefer; if you want to avoid this, but feel you've over-saturated the coil, simply pulse the power button once or twice to burn off the excess e-liquid before taking your first draw.
Typically, the easiest things to look out for and the things you might notice would be some of the following -
Regular vaping
Sub-Ohm vaping