This is your first step and a very crucial one. You need to really know your co-workers and be able to gauge your office accurately. Find at least three people (this is a rough estimate and the number depends on how big your project is) who are interested in your volunteering activity. Choose people who you know will commit time and energy towards your goal. They have to be equally passionate about your cause, whether it be raising money towards a favored charity, starting a volunteering program, or helping your office go green.