I have possibly two individuals on my family tree with the name of Valentine: Mary Valentine on the Odell/Pettit lines and David Valentine Kennett or Kinnett on the Collins line. I have proof of neither of these connections, only charts that show that someone has at some point in time believed that these people are my ancestors.
Which brings me to one of the most important words when working on your family tree:
Yes, the importance of verifying your information cannot be stressed enough. This is the work of our generation. Find as many documents and sources for information on each ancestor and family member as you can. Start with journals, bibles, letters, and other documents. Verify the information you find with vital records, church and parish records, census records, birth and death certificates, obituaries, wills, land records and deeds, military records, marriage records. The possibilities are many and varied, and will vary greatly depending on the location where your family and ancestors lived, and the time period. Many records have been lost over the years, which is very unfortunate, but whenever you do find information, make photo copies wherever possible. Document where the records were found, cite bibliographies, locations etc.
V is for the magic word in genealogy and family history. V is for Verify.