Share 'sourcing sustainably for SMEs - how? what do you do?'

So I'm going to make a wild assumption that many intersecting young professionals are also working in small businesses. (We're only two and a half in my marketing co. ) Without having huge resources to research all day or significant power to influence, How do you make the best purchase decisions and influence change through our small demand. Ie. how do you decide about office supplies, compute…