I'm currently building my startup, and I see other companies having great copywriting, for instance basecamp, Dropbox etc.. Who does their copywriting? How do I find a good one? I have tried a few copywriters but it seems that I know it better then them. I like copywriting to be 'transparent', a little 'funky', with slight humor.
Adding to David's answer, here's another good bet: http://kopywritingkourse.com/copywriters-for-hire/
Network with other marketers and see if they know of anyone who can write the copy you're looking for your sales process/funnel.