There are nearly as many cleaning methods as there are vapers. Some boil their cartos/heads, other's plunge them, some folks rinse with water, or vodka, or everclear. All in an effort to extend the useful life of their hardware.
Personally, I've tried a lot of the different methods (with varying degrees of success) and have settled on rinsing my tanks, tips and caps (which tend to be the non-absorptive parts) and when a carto or clearo head (now using the iClear 30S which is almost like a carto) I will swap in a new one (to keep vaping) and drop the used carto or clearo head into a tall glass of water to soak. I will swap out that water (with hot tap water) daily, and just let them soak. When I have a half dozen or more that have been soaking and water-swapping for a while, I may toss them into a pot for a final boil (just to loosen anything that didn't break up from sitting in the universal solvent), drain them, shake them out, and stand them next to the exhaust port of my laptop for a couple of days. The warm and dry air from the laptop (especially after a good thermometer shake to get out the water) seems to dry them gently and effectively. Then, they go back into rotation and are tossed if they don't perform.
Replacement cartos and clearo heads are a couple of bucks each and while I "could" simply toss them, I like the idea of having a no-fuss and low-effort method to squeeze some extra use out of them.