Make the circumstances for the student as comfortable as possible. If you are doing a question-and-answer session with your students, sit at you desk or -- better yet-- casually against your desk. This will make the process more informal and let you engage them in conversation.
Tell your students to try to mentally outline what they are going to say before they say it. Often, children will not speak clearly because they are just making it up as they go along.
Help a student prepare well ahead of time for a presentation. Make sure they have done thorough research and have all their notes organized. Encourage them to use handouts and other props in presentations, as this will make them feel better prepared.
Use positive statements when discussing a student's ideas. Avoid negative statements when ever possible. Let your students know that a mistake or occasional failure is part of the learning process.
Encourage your students to expand their vocabulary. Have "Words of the Day" on the board, providing the meaning, definition and pronunciation. If a student uses a weak word like "good," ask him in what way it was "good." This will force him to find something more descriptive, like exciting or delicious. Also promote reading in every way possible.