Early in my days of family research, a cousin on my father's side helpfully wrote to me with lots of information which he had gathered. Actually, he was primarily interested in his own relations but was also covering his wife's McQuay side in addition. He had lots of genealogy experience, lots of names and dates, with lots of assurance.
As I had done with details coming from the enthusiast cousin on my mother's side, I greedily absorbed the new particulars into my own records. I was grateful for this short-cut and thankful that my cousin had been able to travel and consult sources which were out of my reach.
However, such information is second-hand and could be considered "WYSIWYG" - What You See Is What You Get. If the aim for your family history hobby is to have names, dates and relationships all filled in then looking at the tree that someone else has constructed will be good enough. On the other hand, if you want certainty that the data is right, and those people really are your actual ancestors rather than another family with a similar selection of names, then there is no substitute for examining the original sources "DIY" - Do It Yourself.
The family tree from my cousin named my great-grandfather as William Albert McQuay. Other family members had said they thought it could have been Albert William and someone told me his name was Harold! Well, I wanted to have a copy of the birth certificate, which would show his registered name, the place of birth, his parents' names, father's occupation and mother's maiden name, a key bridge linking back another generation.
So, I wrote a letter to the register office of the relevant district giving his details and payment for the certificate search, copy and send service. The reply from the Superintendent Registrar said, "I have to advise you that I have traced an entry which may be the one you seek. However, there are certain differences between the details you have given for the date of birth, forename and surname, and those shown in the entry. [...] Your cheque is returned herewith." Not the right forename, or surname, or date of birth - a dead end?
The happy ending is that after a little more work I had in my hand a copy of the marriage certificate for Albert William McQuay, including his own signature, and the birth certificate for Albert Maquay with enough supporting evidence to have confidence that this was indeed a record for baby great-grandfather. However, where he was toddling around age two at the time of the following census was still a mystery, to me at least.