I just wrote this up in an email for my sister - here's my method:
1) Pop off the white cap at the mouth end. I use the metal part of a binder clip that I took apart, but you can use a paper clip or a fork, or the curved end of a metal nail file, or a small crochet hook - basically any tool with a little hook at the end. Make sure it doesn't go too far into the carto, or you can hook the metal wire and kill it.
2) Run the carto under hot water for 20-30 seconds to flush some of the flavoring out.
3) Once you have several of them rinsed, plop them into a pan of boiling water. I use a metal strainer thingie to keep them off the bottom of the pan.
4) Boil for about 15 minutes, then let them cool long enough to handle them.
5) Use a turkey baster with a rubber pencil grip attached to the end or a baby medicine syringe with the white bottle stopper thingie on it (basically anything that will push the water in and out of the carto) and flush them with hot water for about 30 seconds each - I usually run the water through them until it comes out clear.
6) *Optional* soak them in alcohol for about 15 minutes - this can be any alcohol that is safe to consume and has a high alcohol content. I use Everclear. This step is only necessary if you are planning to use one that contained strong flavor for a completely different flavor (like switching from Peppermint to Peach or something). If you keep to the same flavor-family (mint to mint, fruit to fruit, dessert to dessert, tobacco to tobacco, etc) then you can skip this step entirely.
7) Blow through the battery end of the carto to get some of the water out.
8) Put the battery end into the spinner thingie and whirl it around for about 30 seconds. Either put one of the rubber condoms back on the carto or do this outside. This gets most of the water out. Many people have success with refilling directly after this step.
9) Personally, I think there's still too much water in the polyfill at this point, so I either sit them mouth-end up and let them dry for 24-48 hours, or pop them in a low-temperature oven (200 degrees or so) for about an hour before refilling.
10) Refill using the drip technique (like in Snow's video without the audio). Just drip about 6 drops around in a circle (holding the carto at about 45 degree angle), let it soak in, then drip 2-3 drops at a time until they soak in. The cartos will hold ~25 drops. If you get leaking out of the bottom before you hit 20 drops, then there's probably a burn hole in the wick tube, and you probably need to toss the carto, as it won't vape as well and may leak.
11) The cartos can be refilled several times before they need to be cleaned, as long as you quit puffing on them before you get a burned taste. General rule of thumb: the carto will probably need to be re-filled around the same time as the regular length battery dies (3 hours or so of consistent use). If you keep some juice on hand and remember, you can top them off every couple of hours and keep them going for a LONG time. Clean only when they get hard to draw on or start to taste funny.
12) If you really want to replace more cigarettes with vaping, go up a notch or two in the nicotine level. 18mg - 24mg is probably a good starting point for someone smoking over a pack a day. Keeping some 36mg on hand and pulling it out when a craving hits is a good idea also. When I got serious about quitting I went to 24mg for 3 or 4 weeks before dropping to 18mg (mainly because I was vaping so much that 24mg was too strong for me). Dave is still using 24mg, and has no intention of stepping down anytime soon (but he doesn't use his battery for a pacifier like I do). I keep 24mg around and use it in the mornings sometimes, or when I know I won't be able to stop to puff for a while.
13) Another tip for cutting back - when you start craving a cigarette, take 10-15 minutes to do nothing but vape. Then wait 5 minutes or so and see if you still want a cigarette. If you do, then have one... You'll likely find that you don't want more than one, and may not want one at all. Cigarettes have a pretty much instant effect - thanks to all of the carriers that cause the nicotine to freebase and become immediately available to the bloodstream, such as formaldehyde (!). E-liquid has none of that, so it takes a bit longer to get the nicotine's effect. Try holding the vapor in your mouth longer before inhaling, since it is believed that the nicotine in the vapor is primarily absorbed by the soft tissue in your mouth, nose and throat rather than by your lungs.
Hope this helps!
~krashnash