At a recent charity auction I noticed two distinct ways to hold a microphone and two distinct and different results. One speaker held the microphone close to his lips – almost as if he was kissing the microphone. He was loud and easy to hear and understand.
The second speaker, unfortunately the Master of Ceremonies, held the microphone down and off to the side. As a result he was hard to hear and understand.
The other unfortunate situation was that the PA system wasn’t tested adequately ahead of time. You as the speaker or MC need to personally test the equipment as soon as you arrive at your venue and if there is a problem talk to the leaders to get it fixed.
I would also request feedback about your performance every time, so that you can improve and correct problems. I like to phrase it, “What one way can I improve to have a better performance next time?”
southcountytoastmasters.org 
I’ve read that a handheld microphone should be held a few inches from your mouth/chin area.
The PA should be tested beforehand, and adjusted (not through testing) once the audience is in place. Someone should be at the rear of the audience and provide feedback to whomever is at the PA’s control panel. Sound is different in an empty room as opposed to a room full of people.