Do:

• Explain that you have a different opinion and ask if you can voice it.
• Restate the original point of view or decision so it’s clear you understand it.
• Speak slowly — talking in an even tone calms you and the other person down.

Don’t:

When your body language communicates reluctance or anxiety, it undercuts the message. 

Simply slowing the pace and talking in an even tone helps calm the other person down and does the same for you. It also makes you seem confident, even if you aren’t.

It’s a smart way to give the powerful person “psychological safety” and control. 

You can say: “ I have reasons to think that won’t work. I’d like to lay out my reasoning. Would that be OK?” This gives the person a choice, allowing them to verbally opt in.

When you move on to expressing your concerns, watch your language carefully. Avoid any judgment words that might set off your counterpart. Share only facts.

You may decide to hold off voicing your opinion if you want to gather your army first. People can contribute experience or information to your thinking — all the things that would make the disagreement stronger or more valid. 

Also, delay the conversation if you’re in a meeting or...

Articulate the other person’s point of view. 

Stating it clearly, possibly even better than your counterpart did, lays a strong foundation for the discussion. You want your counterpart to say: "She/He understands."

Emphasize that you’re offering your opinion, not gospel truth. Remind the person that this is your point of view, and then invite critique. This will leave room for dialogue.