1. Keep the cotton FLUFFY
One of the most important things to keep in mind is that densely-packed cotton won't soak e-juice up as effectively as a more loosely-packed wick.
2. Don't use too much cotton and Think about your PG/VG ratio
If you use too much cotton for your wick, it’s much harder to ensure it doesn’t end up too dense to wick effectively. Try to thin the cotton on the two sides a little more with scissors.
The amount of cotton you need to use is closely-related to the PG/VG ratio of the juice you'll be vaping. For higher-VG mixes, less cotton is better. This is because VG is thicker than PG, and so needs more“space in your wick to soak up into – a little bit like how you might be able to drink coke through a straw easily but would struggle to enjoy a thick milkshake through it.
If you have a higher-PG blend (like Black Note's 50/50 mixes), then you can afford to have a little bit more cotton packed a little more densely. You still should be able to insert the finished wick into the coil without misshaping it, but you don’t have to be as strict about the amounts.
3. Cut the wicks down
The easiest advice is to give your wick a “bowl cut”around the edges of the deck.
4. Keep the cotton away from juice channel and air hole
Use a small tool (a precision screwdriver, pair of tweezers or anything else small and thin) you can nudge and position your wick to ensure it stays clear of the under-coil airflow hole.
5. Prime the wicks before refilling and vaping
Take a second and give your wicks a liberal soaking in e-juice prior to filling your tanks and you won’t get a dry hit as soon as you start vaping and ruin your hard work.