It is very easy in genealogy research to jump to conclusions, especially when you are just starting out. Pay special attention to family stories and legends, because while family members are usually your best source for information on your family history, memories often become faulty or exaggerated with time. Such oral histories should be confirmed with actual records and documents. The same goes for printed sources - just because a family genealogy or record transcription has been written down or published does not necessarily mean that it is correct. You should never make assumptions about the quality of the research done by others. Anyone can make mistakes, including certified genealogists.

Go over your research with a fine-tooth comb. Is it possible that you have misinterpreted something someone has said or written? Have you made assumptions without sufficient proof? Intuition isn't always wrong, but it isn't always right either.

In Henrietta’s case, I had made one major false assumption – that her maiden name was MARIN because her daughter said so. This daughter, however, was afflicted with typhoid fever as a young child and had always been slightly confused about facts and events in her life. The day she shared the information with my mother in my grandfather’s hospital room, she wasn’t positive about her mother’s maiden name, saying only that it was “something like MARIN.” In my previous research I had searched every bit of Pitt and Edgecombe counties in NC for a MARIN family that could have belonged to my great-grandmother. I had even searched the obvious variations, such as MARTIN, but with no success. It was finally time to drop that assumption and start fresh – assuming that I had no clues to her maiden name at all.
 

For more information:

Top Ten Genealogy Mistakes to Avoid
Ten key mistakes that you will want to avoid in your genealogy research, plus hints, tips and strategies for a successful search.\

Documenting Your Sources
Keep your research on track and create worthwhile genealogies with these tips for documenting your research, including proper source citation techniques.

Jumping to Conclusions
Michael J. Neill explains how making assumptions can create a brick wall, and how to avoid it.