I had someone in this thread do some custom work for me, and was really happy with the end result. I would say that I reached out to 5 or 6 people whom had released several (or more) hacks on this site and had a few responses. I knew that my requirements document needed to be well written and if it wasn't, I wouldn't get what I wanted, and the coder would get fustrated with having to re-code things that weren't well explained, and also with not being able to understand what exactly I needed.
So from a standpoint of hiring someone to do some custom work, you need to definitely document and explain exactly what you need, need to have a good understanding of vb in order to get it across properly, and be willing to be available for conversations (whether on phone or in an IM app) to explain questions that the coder may have. When creating your requirements document, in addition to describing what you want, it may also help if you can make graphical mock-ups or examples to better get the point across of what you want. Remember, a coder can only code what he understands it is that you want, and if you don't properly explain it, he may give you the wrong thing and both of you will end up unhappy. Communication is extremely important.