My cartomizer is leaking

A leaking cartomizer does not instantly mean you have an old or "bad" cartridge; a number of factors including transportation, storage and changes in temperature can lead to a leaking cartomizer.
Luckily there is an easy fix for this, simply hold the cartomizer upright (connector facing down) and roll it between your fingers for around 30 seconds. The e-liquid will now have re-absorbed into the cotton and you should now be able to use your e-cig without any leaks.