Well, it depends on how I've read the room. Note that my line of teaching was EFL, so a little different from regular school or even university. If it's a class of people who are already engaged with each other and talking I'll probably refocus their attention by simply beginning my lesson without speaking or instructing them. I generally accomplish this by beginning to do something on the board.

Sometimes I won't speak at all, instead eliciting responses from students to get them to work together to figure out what I want them to do.

If it's a quiet class, I might hand out a script that students are supposed to read to a partner standing across the room from them. They aren't allowed to move closer together or to spell the words, or mime anything, but they can describe what they mean. Then as they become comfortable, I'd turn on the radio and increase the volume until they're forced to shout as loud as they can.

Of course, afterward, I would give some kind of explanation of the methods used.

In language learning, people expect to hear words, or to write them. The biggest obstacle in language acquisition is not memorizing words or structures, but really the learner's own hangups and fears of being perceived as foolish. The next biggest obstacle is getting students to understand that communication is the core of language learning and that communication is more than simple words or grammar.

When things go "as expected" it's easy to begin fudging details and in a learning situation, particularly language learning, that's not desirable.