Of course number one is don't buy crappy or mystery cartos. And buy appropriate ohms for your device. I don't know what your model's threading is but the most popular cartos for 510 threading are Boge.
Then you need to choose your juice properly. 100% PG juice makes thin vapor. Even 10% VG will make a lot more vapor. But I don't use too much VG - I am using standard resistance cartos and if I use more than 20% VG I can feel the drag get sluggish (people who are using dual coil or LR ir other hotter cartos may be able to use higher VG). So I use 80PG/20Vg and 90PG/10VG in cartos. Boges give me plenty of vapor for a week to 1.5 weeks. The KR808D-1 models I vape give less vapor but more hit with the same juice.
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How I fill Vapor4Life KR8 cartos and Boge 510 cartos
Pop out the soft cap with an unbent paperclip in the mouth hole, very careful not to catch stuffing or the wire loop.
Shake and open the eliquid
Hold a bit of tissue on the threaded end hole, tilt the carto, and add 18 drops per ml of capacity into the stuffing (Boges and most KR8 cartos are about 1ml).
Wait 15 seconds or so then see how many more drops the carto stuffing will soak in easily.
Clean up the threaded end, tilt open end down into tissue, puff into threaded end to clear air channel (Boges and the KR8 cartos I use have a defined center air channel and I want to see light through that)
Sop up any loose juice above the stuffing
Cap and let it settle - I lay it on different sides for 15-20 minutes to make sure every bit of stuffing gets damp so I won't singe the carto. if you use thicker juice than me (I use 20% Vg or less) then you may need to wait much longer.
While
vaping, if the vapor gets a bit light or a bit dry or the carto is getting hotter than normal, I take the carto off the battery and add eliquid. I sometimes use a plastic or delrin drip tip as a mouthpiece on Boge and KR8 cartos (not to drip into since the juice would head for the central air channel)
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I never clean cartos. Some succeed, usually by drying them in a 170-200 degree oven for many hours. But some cartos are just crap - they work well for one fill (SLB) and others will work for a week for me (I am a moderate vaper, not constant).