A good cover is essential. It needs to give an idea of the type of story so a reader can make an informed choice about whether to bother reading. Too many authors have amateurish covers that give the wrong impression. After the quality of the writing, I think the cover is the most important consideration.
Yes, I read through my reviews from time to time. If someone has anything negative to say I don't take it to heart. Instead, I try to take it on board as a way of improving future offerings.
I guess most writers find some difficulty in this. Every time I write an emotional segment from a female point of view I run it past my wife for her opinion.
Oh Boy! Where do I start?
Buying reviews. Buying multiple copies in order to qualify for ‘prestigious’ awards. (This rarely applies to self-published works, we just can't afford it) posting negative reviews to other authors' books, (It's rare, but it does happen) book reviewers who charge for a review but never post it. These are my pet peeves. There are more, of course.
Write for pleasure first. If you don't enjoy your writing how can you expect readers to enjoy it?
Join several writing groups. Facebook pages are a good place to start.
Never be afraid or embarrassed to ask another writer for advice. Even the most famous authors will often find the time to respond. The writing community is generally very supportive.
There's a saying: A rising tide lifts all boats. It's very rare to meet a writer who isn't happy to offer support when it's needed.