My tip is to make it easy, people that aren't really interested will not do it if they have to trail all round the building to recycle something. So things like recycled paper bins need to be put next to ever desk if possible but certainly not more than a few feet between desks.
Also make people aware of what your efforts are achieving. An example, if you have a company that collects paper for recycling can they give you a monthly weight of paper recycled by your office (doesn't have to be exact). If you recycle plastic cups find out how many pencils are made with your cups or how many fleece jackets.
Make a chart of how many trees your office has saved or how many fleece jackets you made or how much space in landfill you have saved and stick it to each paper bin ... a visual representation of your efforts goes a long way to getting people involved.