I want to compile some testimonials from my clients so I can eventually put some on the website.  Do you have any advice or resource/article about the process of collecting testimonials from clients.  I assume you should guide them a bit to elicit the best well thought out, well written responses.  

I've just asked people to give me testimonials – I don't offer a lot of guidance, unless we've done several projects together and one went particularly well.

Usually I ask right at the end of a project, though I have gone back in the archives and asked older clients for testimonials. 

Lately, I've been asking through LinkedIn and then posting those to my website as well. That way, the testimonial is recorded in both places.

I also keep an eye on client emails for interesting comments, and sometimes ask to use those outright, and other times ask them to create a more in-depth testimonial based on their comment. 

Otherwise, I prefer not to guide my clients much – I think the testimonials sound more natural that way. There are others who offer a lot of guidance, such as a questionnaire or template response that people can then modify. I've heard of people getting testimonials by conducting phone interviews. I've even seen people who write out the testimonial for the clients' approval, but that seems a bit contrived to me.