-clean and air dry
-replace coils
-check airflow
-check wattage/voltage of the device
-make sure the wicking material is making contact with the coil
From personal experience I can tell that different atomizer/tanks are better suited for different people. When I made the transition into bigger, 'better' tanks I first bought a Nautilus. I went through 6 or 7 (10ml) bottles of juice in 2-3 days, which for me isn't normal. I'd say I probably vaped 20% of that juice, drank 30 % and the other 50% leaked in my pocket (totally made up numbers btw). I replaced the coils and the atomizer itself but that didn't help. I cleaned and dried all the components and let a friend test it and it worked just fine. Then, when I tried it again I ran into the same problem.
I went and returned it and bought a kanger subtank mini and it hasn't leaked once and, of course, it proved to be a lot more satisfying for me. My friend however prefers the nautilus. My advice is, if after cleaning the tank, replacing the coils and all other suggestions that other posters have offered you still run into the same issue, try a different atomizer.