Let me explain "pre-burn". Before sucking on the drip tip, power your battery for 2-3 seconds to try to vaporize the juice, then gently inhale. Do it again, pre-burn 2-3 seconds before sucking on the drip tip. You're trying to vaporize the excess juice in the carto.
See, each time you suck on the drip tip, you are pulling more juice into the cartomizer from the tank. It already is flooded, so you don't want that. Doing a couple of pre-burns, you might vaporize off some of the excess juice in the carto before sucking even more in it. Understand?
It doesn't often work, but it's worth trying to save a carto.