Do your characters wait for about an hour, or a hour? Does it make a difference that the word hour is pronounced without its H? Should I write that my books delve deeply into a history of a very deceitful family, or an history? Are you treating H like a vowel...and do you know any of the answers?
Why I Hate Words That Start with H
You might think every letter in the alphabet is equal, that all 26 of them are totally benign. The truth is, some of those letters are actually ticking time bombs -- and they may have already detonated inside your book. If you think Y is a tricky letter, you've never gone 10 rounds with the letter H.
The problem with H is that sometimes it audibly shows up to the word party, announcing itself loudly and proudly. Other times, it sneaks in with other letters uninvited. Before you know it, H has spiked the punch, set the carpet on fire and done who-knows-what to get A all bent out of shape. There goes your word party...now you're just breaking up fights between consonants and vowels. Before you know it, some reader's bound to call in the Grammar Police (and those guys are totally un-fun).
H is most troublesome when it starts off a word. Brits won't even pronounce it, and all the rest of us have to remember when it makes a noise and when it doesn't. In American English, H is always pronounced in words like hard, head, hand, hell, hair and heavy. It's sometimes pronounced in words like herb, but it's never pronounced in the words hour, homage or heiress. Words might have a hard H, a soft H, an H that can't make up its mind, or an H that pretends other letters aren't already in front of it (H totally takes the limelight in words like whose, for example, but never in why).
And when your H-word appears immediately after a single A, that's when all the trouble begins. It's common to say "an hour" and "an heiress," but the H never rears its ugly sound in those words. What about when you're using words with a hard H? Should you be writing "an history lesson" instead of "a history lesson?"
Do you treat H like a vowel all of the time, or only some of the time...and when do you know the difference?
A Heck of An Arduous Task
As we all know, the word "a" becomes "an" when it comes in front of a word that begins with a vowel. You have to write that your character picked up an apple and put down a banana. But what if she's eating ham or hummus instead?
It all depends on how she's pronouncing it, actually. Because ham starts with a hard H, your character can eat a ham...she can't eat an ham. The rule actually applies to every single word that starts with a vowel. You wouldn't write that after she eats her ham, she goes to the airport to get an one-way ticket, would you? The word one certainly begins with O (you don't need grammar tips to know that), but it's pronounced WON -- with a hard W sound.
So, if I'm writing a history of a deceitful family without an honorable bone between them, I might have a hard time with figuring out how to best present an H-word...and editing it for proper a and an usage is a headache. If you start having trouble with your a and an usage, just read your text aloud. The pronunciation that comes most commonly to you (herb instead of erb, for instance) is the one you ought to use for your read-along grammar check. Whatever sounds more natural to your ear is almost always the right decision.