Stand in front of a mirror. Select three emotions that you want to display clearly and strongly (excited, curious, concerned, surprised, etc.).
Next, you're going to make faces in the mirror. First make a regular excited face - how you might feel if you received a free dinner. Notice where the corners of your mouth are. Feel you eyebrows raise.
Now, dial up the intensity and make a bigger excited face. Pretend you just won a free vacation. Feel your jaw stretch open a little further. You might notice that you took an inhale in when you made the face.
Finally, aim for a burlesque level face. Imagine an anonymous donor just offered to pay all your bills for the next 50 years...and started a nonprofit organization just for you...and offered to take you on a trip to the moon.
Make your face as extreme as you can make it. It will look completely ridiculous and you'll be able to feel all the muscles in your face working hard.
See how long you can hold that facial expression. 10 seconds? 20? 60!?
Performers do this before a show, and choreograph the specific note or lyric in a song they reveal their expression.
Before you give a speech or presentation, practice this exercise, and select a few key moments when you want to exemplify a strong, specific emotion. You most likely won't use a burlesque level facial expression, but try increasing the intensity of your facial affect to help get your point across.