Especially for memos, agendas, and group emails, add a TL;DR (too long; didn’t read) summary.
Follow this formula: Who does what by when and how are we going to track progress. Write this person by person if needed. If the TL;DR clearly summarizes everything, send only the TL;DR.

People-proof TL;DR

Things that are rare and dwindling become more attractive and are perceived as more valuable. The less we write, the more valuable our writing becomes. 
Refrain from responding immediately. If another recipient should answer, give the person the right of first response. Ask yourself:
<ul>
<li>Do I need to send this now?</li>
<li>If not, do I need to send it at all?</li>
<li>If so, does more than one person really need it?</li>
</ul>

Write less often

Communication is eighty percent listening and twenty percent talking.
In writing, ask clear, concise questions, so they know they'll be heard.

"Listen" more

Tell your recipients from the start what you expect.
If they need to read and comment on it before a Tuesday afternoon meeting, instead of "Agenda for Tuesday," use "PLEASE COMMENT: Agenda for Tuesday."

Action words in your subject line

Because most of us start rambling with our insecurities - don't try to write a final draft on the first try. Allow yourself a few first drafts, then flip it.
Take the final sentence, the conclusion, and move it to the top. This inversion forces you to lead with the need. Then, you'll find that you can eliminate much of the rest.

Lead with the need

When you discover problems, don't compose an email with a long explanation, opinion or instruction as this will make co-workers less inclined to take ownership.
Instead, use one or two sentences to describe the situation, then ask a single question and let the team contribute.

Don’t answer, ask

We long for clarity and for other people to say what they mean in as few words as possible.
Making wordy sentences that lose their fluency due to needless complexity in a text negatively affects the receiver of your message. In short: big is bad.

Fewer words

Nobody wants to read anything you write at work. It's not personal though. We just happen to live in a world where there is so much information asking for our attention.
We can take action and make it easy for our colleagues to read our emails, messages, texts, and memos.

Too much noise, too little attention

Put yourself in the other person’s shoes and ask, “What’s in it for them?” 
When we seek assistance or buy-in, asking for an opinion produces a critic. Asking for advice provides a partner.
Pay attention to your pronouns as well: "You" is selfish. "Them " is selfish. But "we " means working together.

"You", "them", "we"

Long emails and dense, difficult to decipher memos mean modern office communication goes ignored more often than it's understood. For over a decade, I taught college students how to communicate in professional settings. Every class began with a single, all-consuming thesis: "Nobody will ever want to read anything you write at work.