I was saved from the first by the friend, visiting from overseas, who sold me on the joys of ancestor hunting. When I said I was interested, he said "Have you got any aunts or uncles living nearby?" And we went to see an aunt I hadn't seen for 10 years, who had my grandparents' marriage certificate, and as we left he said to me, "They always know more than they think they do."
And I was saved from the second because no one had personal computers in those days and Ancestry.com did not exist.
How to Fail at Family History Research in 10 Simple Steps | Family History Daily:
How to ‘Fail’ at Family History Research in 10 Simple Steps
Step 1. Jump right into your family’s history without taking the time to talk to any of your relatives. Whatever you do, do not ask parents, grandparents, aunts, uncles or cousins what they know about your family’s past.
Step 2. Get a subscription to Ancestry.com and never, ever leave their site. Do not, under any circumstances, check out the many free genealogy websites that contain oodles of unique, helpful information.
But the rest of the mistakes I have made many times, and still do. Read them and be warned.