(Lessons I Learned From Class 1-216)
1. Speak quietly, so your students will have to be quiet to hear you.
Nope! They won't even notice your presence (despite the frantic shushing action of nearby students) and they'll just keep right on talking.
2. Wait for quiet before you start speaking.
You'll pretty much be waiting all afternoon. The noise might briefly dwindle to a dull roar, at which point you'll open your mouth in anticipation, but after that it'll just start back up again.
3. Use a Pavlovian signal to get everyone's attention.
Might be effective the first time, but after that? You're pretty much just the tall(er) lady standing a corner and waving your arms/ringing a bell/shouting "Give me five!"/putting your hands on your head. (All things I tried today. All ineffective.)
4. Be clear about your rules and expectations before delving into your lesson.
Inwardly marvel at the way you hold your students' undivided attention. Savor this moment for later when everything goes haywire. Because it will. Oh, it will.