This drives me crazy, because it's a basic Writing 101 thing, but almost every submission coming in seems to have names that start with the same letter, names with the same number of letters, and names that rhyme.There are also fantasy names the writer made up, but the fantasy name turns out to be something tangible in this world. Google those, by the way, lest you have a hero with a name of a body part in another language!
It's visually confusing, and any editor worth her blue pencil will tell you to change the names to avoid that problem.
I don't care if they're all the PERFECT name for each character. Get over it and put on your game face.
I don't want to see things like Carrie, Cassie, Carley, Charlie, Harley, Ambert, Amber, Emilie, Rosalee, Lorilee, Roderick, Broderick, Jim, Tim, or Slim--get the idea?
(And I flat out dislike "Declan" because half the heroes in romance have that name and it's worn out its welcome, but that's just me.)
I don't care if other writers do it. You be better and smarter!
I got in a submission where the writer said all the same letter names happened in real life, and it was a Family Thing with his tribe. He quite naturally put it into his fictional account of his fun family, thinking it would be amusing. The operational word was "confusing." How can you keep Clem, Clyde, Crystal, Charlie, Carla, and Cory all sorted? You can't -- and the reader won't either.
I know, I know J.R.R. Tolkien had all those fun Dwarf and Elvish names and nerds like me adore them. Who wouldn't want to memorize Bifur, Bofur, Bombur, Ori, Dori, Oin, and Gloin or double date Fili and Kili? Well, that was then, this is now. Make sure your work doesn't get bogged down by this problem. Professor Tolkien can get away with it, but you ain't him. You be better!
More often than you'd imagine, writers do this naming thing unconsciously. I sure did and take pains to avoid it. Perhaps the hero's name starts with M and then he runs into a Moira and calls his horse Mordred, and later his cousin Murch turns up, all without the writer noticing. Even long in the tooth writers who should know better make this mistake.
Avoid it from the get-go. Here's how:
Take a sheet of paper, divide it into 26 squares and put a letter of the alphabet in each square.
This is your cheat sheet.
When you name a character, put the name in the corresponding square. You can't use that letter again; it's off the menu.
If you have a large cast, make sure same-letter named characters don't appear in the same scene or they go by a nickname.
However important a name may be to your book, any editor (or agent) who is on the ball and looking out for you will point out same letter names and ask you to change one. But do not trust that your editor has time for that. She's juggling a lot of other writers, so save her some work and take care of this before sending the book in.
The less work you give her to do the more of your work she will want to see.