There are people out there that have information we want. The trick is getting that information when those people are not as passionate about family history as we are. You will be contacting these people by letter, by phone and in person. There are a few tricks that will help you.
When you send letters to people you do not know, introduce yourself by not only explaining who you are but how you are related to them. Do not send a form letter. Make each letter personal. Do not ask for too much information at one time. Always send a self addressed, stamped envelope for their reply. However, do not be surprised if you get no response at all. I have sent as many as 50 letters at a time and maybe gotten two or three responses back.
Whether you call someone on the phone or you visit them in person for the first time, thoroughly explain who you are and why you are calling. Many people are uncomfortable speaking with someone they do not know. If the person knows you are Aunt Mary's second cousin on her father's side, they will be more willing to open up.
People will be more willing to talk to you if you speak to them in a conversational manner instead of shooting questions at them like a Gatling gun. Politely listen to everything they want to tell you even if it has nothing to do with what you want to know. Use a digital camera to take pictures of their old photographs instead of asking to take them with you to copy. Many people are nervous about letting someone take their photos.
If the person is giving you a lot of information, ask if you can use a tape recorder. Then you can give the person your full attention instead of trying to take notes. Always offer the person a copy of the research you have done on their branch of the family. Not only does the person feel as though they are getting something in return for their cooperation, but it just might get them interested in their family history.
Interview the oldest people you know first. It is very sad when someone dies before they are able to pass on the knowledge they have about the family. In 1976, I attended a family reunion in which my great, great aunt also attended. She was 100 years old. At that time I wasn't the least bit interested in genealogy. (In my own defense, I was only 14 years old). Can you imagine what she could have told me had I been smart enough to sit down and listen to her old stories? She died when she was 102 years old, and all she knew is forever lost.
I recommend that you have calling cards printed up with all of your contact information. It is much more professional than scrounging around for a piece of paper and a pencil when someone wants your phone number and address.
Common courtesy and politeness go a long way in helping you get the information you need.