I think the tips in this article ‘How To Connect WIth An Employer On Linkedin‘ by Caitlin Madden can also be used to connect with potential clients if you are a business owner. Although I’m not sure I agree with the advice to contact the hiring manager directly or to try to guess their email address. If contact info isn’t provided, I’m guessing it’s for a reason – you don’t want your business to seem spammy, sneaky or annoying. Other than that, this article provides some useful guidelines and advice.
Check out fullserve.info (a posterous account I use for my clients) for an article about Linkedin privacy controls.