Survey your class to see what types of pronunciation errors there are. If your class is a second language learning class, students will likely have problems with accents and correct pronunciations for difficult words. If your class is full of adults who already speak a particular language, but need help with correct pronunciation, you'll likely have problems with incorrect grammar, abbreviations of words, and saying things incorrectly.
Identify the main elements of pronunciation that need to be taught in your classroom. Design lessons around those things.
Demonstrate the correct pronunciations of words during specific lessons. Allow students to try to pronounce words correctly, and engage the entire class in helping everyone figure out how to say things. Speak words to the students, and then allow them to repeat the words back. Begin by having the students say the words together as a group, and then move into smaller groups. As students move into smaller groups, they can better listen to each other's speech and begin to mimic it.
Allow the majority of your class time to be spent in discussion. When students talk together, they can demonstrate proper usage of speech and pronunciation, and they can correct each other's grammar simply by repeating correctly what they hear someone else say incorrectly.
Engage students in conversations. Set topics and give students questions to discuss among themselves. Talking with other students, practicing the language, and repeating the same speech patterns are good ways for students who are learning pronunciation to create those speech patterns for themselves.