At the B&M where I bought my starter kit, they taught me to prime the coil (Kanger Evod2 BDC) by blocking off the air-holes and sucking on the mouthpiece so the vacuum pressure draws a little juice into the wicks. Other people say to just fill it up and let it sit for (anywhere from half a minute to several hours, depending on who you listen to and what kind of juice you use -- higher-VG juice is thicker and may require more time to "seep" into the wick than thinner juice with more PG than VG.)