The correct strategy can be chosen only by the teacher in special situation depends on class he/she is working in. I'm not really a teacher but I might be able to propose something.
To ask students tend to keep silence during the lesson more often, in a way which, in your point of view, could encourage them to answer. If someone dominates the others try loosening attention to him/her but you should control it, avoiding sharp ignorance, of course. Make it clear in some soft way that there are not only persons who can grasp everything on fly. Try combining some weak students to groups and pay more attention to them and encourage every better step they make. Some games, points, interests the weak like can also improve their oral experience. The teacher is a sophisticated psychologist, at least he/she should be, I guess.