Adverbs are useful! They let you describe how something is happening. Adverbs are words like totally, angrily, obviously, and never that modify verbs and adjectives. You can say something is totally green (adverb + adjective) or someone is angrily hammering (adverb + verb). I'm sure you can see the appeal.
If you see an adverb, kill it.
—Mark Twain
The Problems with Adverbs
They multiply like weeds or empty coat hangers. You let one carefully or quickly in the door, and before you know it your text is full of good-naturedly and stealthily. Where does it all end?
They reduce precision. The usual suspects creep in: generally, obviously, immediately, often. How often? Does immediately mean this week or right this second? Does obviously add any information? What does generally mean, and what are the exceptions? When you find yourself tempted to use an adverb, think about what you mean to say and say it. Specifically.
They affect your other word choices. Which sounds better: she slammed the door, or she closed the door harshly? Hint: the correct answer is not she slammed the door harshly! When you go looking for the perfect adverb, you forget that you have some excellent verbs at your disposal. Worse, you forget that sentences are not isolated. You can get by just fine with She closed the door if the sentences nearby convey her reason for closing it. Adding harshly is lazy and is less likely to bring the reader into the mind of your character.
The adverb is not your friend.
—Stephen King
They can be redundant. If you say something like I quickly ran to the door, the word quickly doesn't add new information. Unless you're on the moon, it's hard to run slowly. Adverbs like really, truly, completely, and very sound nice and seem to add emphasis, but don't change the meaning all that much. In fact, sometimes I'm tired sounds more tired than I'm really tired. Let's not even get started on literally.
Can the Adverb Be Redeemed?
Even the adverb-efficient still use them occasionally. Hemingway, a famously sparing writer, used 80 adverbs per 10,000 words—beaten by Toni Morrison, who used 79. But those numbers are not zero. Heck, I've got an occasionally two sentences ago. By my count, leaving out the ones I've put in as examples, I'm running about one adverb per 100 words in this essay, or somewhat more than the ratio of Morrison or Hemingway.
Yes, there are times when you should use adverbs.
If the instructions say Clean with a damp cloth, we aren't sure whether it would be bad to use soap and water just this once. But adding only tells us not to use anything other than a damp cloth. If your story says that Sam went to bed early, that means more than Sam went to bed. Use adverbs when they add information, flavor, or rhythm. Take them out when they aren't pulling their weight.
To take a few nouns, and a few pronouns, and adverbs and adjectives, and put them together, ball them up, and throw them against the wall to make them bounce. That's what Norman Mailer did. That's what James Baldwin did, and Joan Didion did, and that's what I do—that's what I mean to do.
—Maya Angelou
Some adverbs are good. Some adverbs are bad. Watch out for adverbs in your own writing. When you use one, make sure it's doing a real job. Eliminate the ones that just add syllables.
What's So Bad about Adverbs?
I hate to be picky about a clear, concise article, but your math isn't right, or your statistics aren't.
80 per 10000 is 80/10000 = 0.008; 1 per 100 is 1/100 = 0.01 which is only 1.25 x 0.008.
You are acting with more restraint than you think. (I hope I got this right.)