The humor one is big for me, especially since I have a more twisted & absurdist taste in terms of comedy. I make myself laugh a lot more then other people, so finding a joke that hits is hard.
Beyond that I've also had to censor my vernacular to make my work more palatable. I'm from NY & my books take place in parts of the city that have a very particular way to speaking( slang, cussing, ect). The majority of my first drafts could only be read by other New Yorkers. I had to cut out quite a bit before I found things more people could relate too who were from outside of my city.