If you use a new atomiser or tank straight after filling before priming it, you may get a burnt taste, and your coil may be un usable.
To avoid this, let the atomiser sit for a couple of minutes to make sure the liquid is absorbed by the wick before using it.
With bigger coils it can take some time to prime the coil. This is done by applying liquid to the exposed cotton at the base of the coil, as well as dropping some liquid down from the top of the coil to soak the material around the side and allowing the coil to sit in the liquid for at least 15 minutes. Do not over saturate the coil as it may flood. The aim is to make sure none of the wick is dry, so it is less likely to burn.