I recommend 'Customer Service for Dummies'- 3rd Edition by Karen Leland and Keith Bailey. This is a must have for all Virtual Customer Service, Sales Reps and Property Managers, in your reference library. Whether you're conducting business in-person, email or phone, you'll find plenty of suggestions and tips. The book includes sales techinques, as well.
Some of these tips are as follows:
Paraphrasing or backtracking lets the customer know that you heard them.
Use open-ended questions to produce positive results.
There's even a chapter for on how you can receive get great customer service! The book sells for $21.99 but I would definitely shop around.