If you are manipulating/twisting at all to get cotton through your coil (which maybe isn't necessary with cotton, cotton never wanted to cooperate with me so I kicked it to the curb for it's cooler older sister, rayon, LOL) make sure all fibers are untwisted and straight in the coil, and reduce (most likely) the amount of cotton in the coil, it swells when wet. I don't think it's impossible to get "too much" in the coil (either with cotton or rayon, although rayon shrinks when wet) but I tend to want to overstuff my coils far more than necessary, and since literally wicking everything while saying, "This thing is going to leak," well, I no longer have wicking break inside my coil.
Wicking is kind of weird, you'd think "more is better" for stopping leaks, but that is not always the case (although it can be on some atomizers) and I've found that coil and wick placement matter a whole lot more than "how much" wick may or may not be present, and with some tanks, less is most certainly more. Same with wick tails, too thick and capillary action will actually be reduced meaning more dry hits, as it's hard for the cotton to stay saturated. With rayon, I still use a fair amount in the coil, but I make sure it's not distorting in any way, and will sit, but with slight pressure and tugging begin to move. I also make sure to thin and trim my tails a fair bit.
I do think watching some tutorials may help. I do that with most new equipment I get, watch a few reviews, less for the reviewer's opinion and more how to get the best out of my equipment.
There are many wicks beside cotton and a whole host of different types of material. That was certainly part of the puzzle for me, figuring out what wicking material played to my "strengths" as it were, and that just happened to be rayon for me. I'm not saying you have to go out and get rayon right this second or anything, but along the way it can be fun to try different wicking materials and learn the differences. You may find cotton is "the best" for you once you learn how it handles, or you may find out down the line (if you even want to experiment) that another wicking material works best.
Best of luck,
Anna