Starting off each class with an ice-breaking exercise will keep the lessons fun, allow the young adults to get to know each other and promote their communication abilities. Each class, ask one student to prepare three facts about themselves, one of which is a lie. They will then deliver it to the class, who will have to guess which is the lie. This is an enjoyable exercise, and will make the students more confident in speaking in front of people.
Give everyone in the class a topic, and ask them to prepare a presentation on the subject. Do not tell them how long the presentation will be until they are about to begin. Times can range from 10 seconds to 5 minutes. This will force students to learn the salient points of an issue, and be prepared to think and communicate on their feet. Prioritizing information is an important section of communication.
Having students analyze others' performance will help them improve their own techniques. Get a video clip of a good speech and a bad speech. Play them to the students and ask them to comment on the positive and negative aspects of each. If you can get hold of the transcripts, ask the students to do a better job than the bad speech. This will improve both intonation and delivery styles, and make students aware of what is bad communication and what is good.
Since such a large amount of communication is non-verbal, have the students play a version of charades. Send all the students out of the room, and bring them in one by one. Act out the name of a famous book or film to the first student, and have them act it out to the next, and so on, until the last person. Have the last student tell you what they think the name of the book or film is.