Business writing is about clarity and persuasion. The main technique is keeping things simple. Simple writing is persuasive. A good argument in five sentences will sway more people than a brilliant argument in a hundred sentences. Don't fight it.
Simple means getting rid of extra words. Don't write, "He was very happy" when you can write "He was happy." You think the word "very" adds something. It doesn't. Prune your sentences.
Humor writing is a lot like business writing. It needs to be simple. The main difference is in the choice of words. For humor, don't say "drink" when you can say "swill."
Your first sentence needs to grab the reader. Go back and read my first sentence to this post. I rewrote it a dozen times. It makes you curious. That's the key.
Write short sentences. Avoid putting multiple thoughts in one sentence. Readers aren't as smart as you'd think.
Learn how brains organize ideas. Readers comprehend "the boy hit the ball" quicker than "the ball was hit by the boy." Both sentences mean the same, but it's easier to imagine the object (the boy) before the action (the hitting). All brains work that way. (Notice I didn't say, "That is the way all brains work"?)
That's it. You just learned 80% of the rules of good writing. You're welcome.