When you work with customers you should be putting your best foot forward and giving them all your attention while working with them. Your job is to keep the business relationship through excellent work and service. It is when you are at this point that you can ask for a reference letter for your library. You will find that most customers will be happy to give you a reference letter but they will not likely volunteer it, you will have to ask. Often you will have to write the reference letter yourself and send it to the customer to edit and put on their letterhead. References are always important; they can help you obtain further business. Reference letters also show that customers are happy about what it is that you do for them. If you go to most professional websites, they will have a place for testimonials. These testimonials are from their happy customers who are glad to blow your horn.

If you blow your own horn, there is less credibility than if someone else does it for you. There is something about having a third party talking about you that is more credible than what you "the expert" has to say about yourself. The third party endorsement is used all over in advertising. You often see "stars" promoting products - they are being used as third party endorsers. You may also see items such as "This is what our customers say about us". Even though it is not a guarantee that you will be good on the job, it just lends a little more credence to what you are saying.

The important thing is to keep consistent with your message. Even the references and endorsements need to be the same message. Without consistency you will run into being deemed a "general" practitioner that does not have a specialty. This in turn will downplay your expertise. Consistency will keep you in the forefront and people will remember who you are.