The first item you’ll need is blank cartridges or old used cartridges. Each cartridge comes with polyester wicking material that holds the e-liquid. The wicking material should be changed after 8-12 refills. Also keep in mind that combining different e-liquids using the same wick will produce some unusual flavors which may or may not be desirable.
Before you refill electronic cigarette cartridges, remove the wicking material.
Dispose of the wick if you’ve already refilled the electronic cigarette more than 12 times.
Boil a cup of water in the microwave oven. Remove the cup from the microwave and put the empty electronic cigarette cartridges in the boiling water. Let soak for 10 minutes.
Prepare new wicking material. The wicking material must be 100% virgin polyester. 
You can buy 100% virgin polyester from a number of local sources and then simply cut to size as you need. Walmart sells something called “High Loft Quilter’s Polyester Batting” from Morning Glory in the craft area. Make sure it is 100% polyester. You do not want any mixes with cotton. Also make sure it is NOT treated. You do not want to vape fire retardant chemical. The best way to tell is to look for a warning label on the bag. If it says the product is “fire safe”, DO NOT BUY because it’s been treated. You want 100% non treated polyester. Buy the smallest bag (cost under $5) and you should have enough to last the rest of your life.
Take an original clean wick and use it as a template to cut the polyester into new wicks. In 5-10 minutes you should be able to cut a bag full. It doesn’t need to be an exact science. You just want the new wick to fully fit in the cart fairly tightly, but not too tight so the liquid cannot seep through.
To fill or refill the wicks, you can use an eye dropper or a syringe with needle. The best is a syringe with a needle. A syringe will fill your cartridge from the bottom up while an eye dropper will fill from the top down. Most e-liquid you buy will come with a dripper bottle or an eye dropper.
If you’re filling from the top down with an eyedropper or bottle consider a little trick I discovered to really top off the refill electronic cigarette cartridges. Take a small coffee straw and cut it to fit inside the cartridge. Slide it into the electronic cigarette cartridge between the cartridge and the wicking material. What this does is provide an air release from the bottom of the cartridge as the e-liquid soaks into the wicking material. It works very well to help completely refill your electronic cigarette cartridges. Just be sure the straw is cut low enough to fit in the cartridge but high enough so the e-liquid doesn’t cover it.
It’s extremely easy and will save a bunch of money if you learn these easy techniques. Buying your own e-liquid from a reputable source and doing your own electronic cigarette refills is by far the best you’ll have with electric cigarettes.
