After I posted the font discussion, I realized that I probably should have talked about this first. You’ll be working with fonts throughout the entire process, of course, but the easiest way to design a book is to start with the cover and work your way in.
First of all: as many have said before me, if you’re really serious about making your book as professional and effective as it can possibly be, hire a professional graphic designer. Book covers are a work of art. So hire an artist. And don’t go telling me it’s too expensive, if you’re serious about making your book good instead of just throwing it haphazardly to the wolves, you will get a designer. Even if that means calling in a favor from an art school friend who’s technically an amateur.
I am not a graphic designer, therefore, I really can’t tell you how to make an effective book cover. All I can do is give you a few quick Dos and Don’ts on the subject of book covers in particular.
First: DO come up with several different ideas and try out several different designs before deciding which one is best for your work. There’s lots of different cover styles out there. Some use human models. Some use illustrations. Some forgo representing humans altogether and instead use an iconic image to represent the entire story. Figure out what suits your novel and your genre and go with it.
However, DON’T imitate the cover of a popular novel that is like your book. One of the things you could say about Twilight is that it had a fantastic cover design; but since then there’s been so many copy-cats that nearly all red-on-black designs with white letters are going to look like is Twilight knock-offs, even if they’re not. (Don't get me started on those Wuthering Heights "FOR TEENS" editions...)
DO make sure you own the rights to the images on and in your book. Either take the pictures yourself or double-check the reproduction/copyright restrictions on the stock photos that you pay for. It’s just going to save you a lot of trouble.
DO make sure that your title works with the rest of your cover. There’s a lot of self-published books that just slap the title over the picture, and it looks really lazy. Try to make sure that the whole cover works together.
DON’T make your author name larger than your title. In fact, as a general rule, your author name should be much smaller than your title, at least by half. Remember, the title is the important part.
I know that there are lots of books out there that have big author names, but those books fall into two categories: 1) The author is a guaranteed best-seller who has proven that even their crappy books will sell, so the fact that they wrote it is the biggest selling point (see: the first edition of Stephen King’s first novel, compared to his more recent books), or 2) we’ve got a major case of Small Name, Big Ego going on here.
In the world of self-publishing, the truth is usually the latter.