For the following activities, it often helps to break the group into couples or trios. The smaller groups allow for more discussion, keeps participants from mentally wondering off, builds rapport, and allows for "one-on-one" relationships.
You can also break a large group into small groups by having them discuss the activity with the person behind them, or having people take a different seat when they return from breaks or activities. The idea is to get them to meet and learn about other people besides their friends or favorite partner.