Letters to send out to past Customers to get their business back. Need to make a good impression.?

Can someone please tell me some websites that will give me some templates or sample letters to send to past customers that haven't been buying for a while. Also some example surveys that I could send out with the letter. Any ideas that i could use for the letter would be greatly Appreciated. I need something that will make the customers start coming backi again and I have no clue where to begin and I need to make a good impression on my boss.