What helped me was when I settled on a coil diameter, my case was a 2.5mm Coil Master, and a wicking materal, KGD. Then I just experimented with all different kinds of widths of cotton, starting at 3mm in width and moving up the scale to about 15mm in width (very tight) and keeping notes as I went. I used the same atomizer/mod/wattage for my testing so as to keep the variables down to just the width of my KGD cotton strips. When I had something That I thought was a good, repeatable build, in my wattage range, I tried it in a different atomizer to see how that fared. It was a process for me to learn wicking. As long as you're Hardware is working as it should (mod/Atomizer) then it leaves you're build as what will make or break you're vape. I found that if I went from a verticle, to a horizontal, to a Genny, to a Magma and so on while trying to get my wicking down, it just confused me to no end. I had to start with 1 atomizer and keep on it till I got it right, cause each atomizer is just a bit different to get right.