Don't get e-liquid down the center tube. This can cause issues by flooding the coils with too much liquid and creating a mess.
Take care while filling. Using an e-liquid bottle with a fine tip can help with more accurate dispensing of the vape juice and avoid spillage.
Respect the top marking on the tank if there is one, spillage can occur if you overfill your tank.
However, if you overfill your tank, the best thing to do is to detach the tank from the battery, use a paper towel to soak up the excess e-liquid, and blow through the airway to clear any additional extra fluid.
Make sure to let the vape juice soak into the tank’s wick for 5-10 minutes after refilling. This will help you avoid having a burnt taste when you power up your device again..