How should I open a business letter?

When you write to a customer, your correspondence is telling him about you and your company - about your professionalism, your interest in serving him, the style with which you conduct business. Just the thought of getting started can strike terror.
In order to help you to write routine letters, here are some examples of opening sentences .....

It was a pleasure meeting you last week, and I thank you for the opportunity to introduce you to our ......
Thank you for your request for more information on .....
It is with great pleasure that I introduce our newest sales engineer, Mr........
In response to your recent inquiry, we are pleased to submit the attached quotation for.....
I'm writing yo make sure that you received our proposal for your .......
I'm enclosing our revised proposal for the ......
I would like to confirm the .....
We confirm that the .....
Effective March 3, we're forced to increase the dealer's price for.....
I'm sorry I missed our meeting last Tuesday. As i explained to your secretary over the phone, ...
As I stated on the phone, the information in your files relating to our ....
As we discussed on the phone, we look forward to you providing ........
We're sorry to inform you that we did not choose your ......
Enclosed is ....
In response to the ....
Thank you for letting us know about the .....
With reference to your ......
We very much regret the ....
Following your instructions of (date), we have.....
In accordance with the request in your .....
According to our .....