Practice jaw exercises to enhance clarity of speech. Use a mirror to aid you in this step. Here are three exercises to help. These also help relax the jaw, making speech a lot clearer:
Make wide chewing motions while humming gently.
Stretch every muscle in your jaw and face. Open your mouth as wide as possible (as if you were about to yawn), while moving your jaw in circles, and sideways.
1、Open your mouth wide, as in the previous exercise, and shut it again. Repeat 5 times.
2、Try tongue twisters. Start off slowly, and gradually build up until you say them at normal conversation speed. When speaking them, exaggerate the words, making your tongue, jaw and lips work hard. As you become surer of them, begin to project your voice and exaggerate the words more. This helps you gain skill.
3、Have a conversation with yourself in front of the mirror. It may sound silly, but it does help. Again, exaggerate your words as you speak.
4、Gargle some lukewarm water with a pinch of salt. This helps relieve tension in the throat.
5、Avoid speaking with clenched teeth.
6、Don't rush when speaking. Talk deliberately, but not so slow that you are a robot.
7、Swallow excess saliva. Saliva left in the mouth can result in mumbling and distortion of consonants such as "S" and "K".