Interviews are a great way to gather information concerning a moment in your life from another person's point of view. You can interview family, friends, and other sources that may have information relevant to your memoir.
Here are some great online tutorials for interviewing:
Although they are on how to conduct video interviews, these how-to videos from eHow.com have good points about interviewing in general:
Here are some useful web sites containing biographical information on famous people (in case your memoir mentions a famous person):
Depending on your topic, you may find it helpful to locate resources on statistics and surverys, which are often conducted by news agencies, non-profit organizations, government agencies, and marketing firms.
The following resources contain surveys and statistics: