We've all heard the mistaken idea that "if it's in print then it must be true!" If you are working to preserve your family history, make sure you don't pass down wrong information that will forever be accepted as factual.
The most important rule that we should follow in putting together our family history: The sources of our information should be reliable! Just because you may find a family tree on the internet in no way means it is even remotely correct. To know that your information is correct you have to PROVE IT! Sure, information found on the internet (such as this site) or in libraries will help you put your family history together, but that information should be considered reliable only if a reliable source is cited for each piece of data. I have no doubt that some genealogical information presented on this site is wrong (gasp!). That is why I have ranked each source from 0 to 4, 4 indicating that it is "convincing evidence".
You are responsible to yourself and to your descendants to study these sources for yourself and be able to come to the same conclusions before you publish your work.
Example of Reliable Sources*:
In short, the most reliable sources are those that were created closest to the event, such as an official birth certificate to prove a date of birth, or a marriage license to verify a marriage.
Good luck and have fun researching!
*Reliable is a relative term...I have found even these to be incorrect. The more sources you can find for each piece of data the better!