I thought that "Brainstorming" was an interesting concept to examine, it can be used as an initial activity as can be used for a large class, getting everyone involved is key.  They would all fell included and their contributions appreciated.  Brainstorming can be used to look at a concept such as money, students will give their ideas as to what is money, possible give suggestions as to items that were previously used as money or possiblly the characteristics of money.