This week I thought I'd look at mistakes and offer my list of the top five mistakes I think new authors should try avoiding if possible.
1) Rushing through the Editing Process
When you rush through editing, you take a huge rick that you'll be leaving mistakes in your manuscript—mistakes that may cause readers to leave bad reviews...which may lead to fewer sales. And nobody has time for fewer sales and bad reviews.
Additionally, lots of mistakes in your book just looks unprofessional. Come on, we as indie authors have enough of a hard time getting our books in front of readers because of the false stigma that indie books are of lesser quality than traditionally published books. Why give the naysayers something to point to and say, "See? I told you so!"
2) Taking too long to edit — never ending the edit
On the flip side of rushing through the editing process, the flip side then is taking TOO long. There has to be a stopping point where it's "good enough," and you can hit publish and move on to the next book. You do want to be published, right?
If you edit and edit and edit, you can easily spend a month on one paragraph or even one sentence to make it perfect. But over-editing can also strip your book of the excitement, the passion that made the story great. After all, the idea was good enough for you to want to spend countless hours pounding away at the keyboard...why edit it until it's grammatically perfect, but so flat that it's just...boring?
Why? Because your book is never going to be perfect for all readers, so make it good enough and move on to the next story!
The trick is knowing what's "good enough." I can hear you now: "But how will I know?"
It's kind of like when you fall in love. When you know, you'll know. Or you'll get so sick of the story you'll call it good enough whether that's true or not. Knowing your story is ready for publication will come through experience...and don't worry, for good or ill, your readers will tell you.
3) Responding to reviewers who didn't like your story
Hooo-boy this one's a doozy. First off, this rule is simple. Don't do it. It's unprofessional. Arguing or pointing out the flaws in a reviewer's comments—even when it's clear they didn't read your book—makes you look just as foolish as the fool who didn't read your book (write long enough and I guarantee you'll get a reviewer that trashes your story and makes it painfully obvious they were totally ignorant of what the story was about).
Arguing with readers will lead to nowhere. At best, a disgruntled reader (and others reading the exchange) may be turned off by a sour-grapes author...at worst, you'll look like a petulant kid and that will turn off even more readers.
There's just no point.
Instead, I suggest you use the bad reviews (except the ones where they didn't read the book, those are useless...laugh at them and keep scrolling). Make a note of what the reviewer criticized, like your spelling or dialog. If others mention the same thing, they might be on to something...remember, you can't please all the people all the time, but you should try to please most of the people most of the time.
4) Not pricing your books at an honest value
I'm pretty sure someone will argue with me over this (and you can watch me avoid Mistake 3, above). And that's okay—we can all have different opinions. I'm just telling you what works and makes sense to me.
I say your time is valuable, its the only thing you can never get more of. You can't be afraid to say "no"... especially when someone asks you for a free copy of your book.
Every once in a while it's totally fine, by the way, to give some books away. However, if you get into the habit of saying "yes" to everyone who asks—or gives you a sob story about how they can't afford your $3.99 book—you may as well just put everything up for free and be done with it, because you're saying if your work is free, it's worth exactly that. Nothing. All that effort and mental strain you put yourself through to create the story, craft the words, and forge that manuscript into a book or story or whatnot will have been for what? If you're fine with that, go for it. But I'm willing to bet 99%—or more—of authors would like to be compensated at a reasonable price for their work and effort...it's only fair.
I wouldn't expect someone to build me a house for free...why would I expect to get a book for free? If we give away our work for nothing or very little cost, we train our readers to expect free or next-to-free. 
Devaluing your hard work by selling stories super cheap (or giving everything away) is something that's very hard to change later on. Writing is a LOT harder than people think, but everyone seems to know it at least subconsciously—or we'd all be writers!
Pricing all your books low doesn't help you in the long run because you'll be training your readers to expect cheap stories that otherwise (depending on your genre) might be going for three, four, five, or even six dollars—or more. 
5) Not putting enough resources into the cover
The old saying is "don't judge a book by its cover," but that isn't necessarily the case with...books. In today's digital marketplace, your book will live and die by it's cover. When readers scroll through lists of books to buy or read on their devices and what do they see? Not detailed blurbs, not tag lines...sometimes not even prices. What they see are covers.
If the cover doesn't interest them, they keep scrolling, it's that simple.
That is so important, I'll say it again. If the cover doesn't interest the reader, they won't buy the book. Period, full stop, end of sentence.
I understand that when you're starting out as a greenhorn author, covers can seem daunting. It's very tempting to make your own. Let me just say right here that if you're not a graphics design professional, I'd highly recommend you hire someone to do your cover. There are reasonable options, anywhere from $5 to several hundreds—or thousands of dollars—depending on options: ebook only, ebook and print, print only, audio book, all of them...merchandising rights, editing rights, the list goes on...
If you take your time and get to know artists, you might find an art student or someone trying to break into the marketplace as a cover designer willing to do your cover for free. They usually retain the right to use your cover to grow their portfolio and attract other clients. You get a free cover, that's hopefully awesome.
The key is to not be impatient—take your time, do your research, and have patience. You didn't write your book in an hour, so don't think you can solve your cover design in an hour, either! Remember, your book lives and dies by its cover...make it a good one, do the research, see what the top books in your genre are doing and try to emulate that.
Note: I don't mean copy the design, just riff on the motiff. In the Thrillers category, for example, a popular design—a proven winner—is the silhouette of a person with the title/author's name tilted at an angle in big letter with long shadows.
If it works for the big name authors it can work for you.
So get out there and spread your wings. Write what you want, write to market, get that book edited and get a good cover...then get started on the next one.
: We'll talk about permafrees and reader magnets later—those don't count because they're marketing strategies...remember, I'm talking about just giving away the farm because it makes you feel good.
: Loss leaders and reader magnets are yet another proven marketing strategy...