Well I did write an entire book on this topic
Seriously though, you are wise to proceed slowly with taking on outside investors. I would recommend doing the following before you even begin negotiating with any prospective investors:
--Sit with yourself and/or all your existing partners in the venture and articulate, VERY CLEARLY, what your values are.
--Write up a formal values statement, and a set of operating principles.
--Define success, in terms of how big the business will be, how quickly it will grow, what your impacts will be on your various stakeholders, who will benefit financially, etc etc etc.
Once you have spent some time with the above, it will be much easier to determine whether you want to expand at all, much less whether any would-be investors might share your vision.
-Elizabeth