It took me awhile to learn this bit of truth:
Never use a verb other than "said" to carry dialogue. The line of dialogue belongs to the character; the verb is the writer sticking his nose in. But "said" is far less intrusive than "grumbled", "gasped", "cautioned", "lied". Never use an adverb to modify the verb "said" . . . he admonished gravely. To use an adverb this way (or almost any way) is a mortal sin. The writer is now exposing himself in earnest, using a word that distracts and can interrupt the rhythm of the exchange. ~Elmore Leonard
I don't know that I'd go so far as to call the use of adverbs a mortal sin, lol, but Mr. Leonard certainly has a point (Stephen King also gives very similar advice in his book, On Writing). For one thing, if the character is angry, we should be able to tell it by the curse word he uses, or by the actual terse wording of his dialogue. Therefore, it's unnecessary to follow up his dialogue with: he said, angrily. That would be redundant.
As a new writer, I was constantly trying to show off my language skills, making things flowery or super-descriptive, thinking I was "writing." But sometimes, as I've mentioned before, less is more. And dialogue, especially, should shine, all by itself. It is about the character. It's about what they're saying to each other, the words they're using - even the words they're not using. Writers shouldn't weigh down dialogue or interrupt its flow by adding too many descriptive (and unnecessary) words.
I say all of this with a caution - because I do think a writer's own natural voice should come through the writing, and I don't wish to stifle anyone's true voice. Some writers are naturally descriptive, even during dialogue, while others are more succinct. Description isn't always bad. There is a time and place for it. In fact, how boring would a long conversation between characters be if it looked like this?
"blah blah blah," he said.
"blah blah blah BLAH blah blah," she said.
"but...blah blah blah blah blah," he said.
So, my best suggestion is balance. Listen to your own gut, READ fiction and see how others handle dialogue (this is key), and then, dive in. Experiment. Read your own dialogue aloud (also key). Most importantly, let everything feel as natural as possible, and if any word or description gets in the way of the conversation, remove it.
Writing is never an exact science. It's subjective. But I think we each have to find our comfort zone and write what comes most naturally to us - keeping in mind the good advice from other writers, such as Mr. Leonard.