Proof Documents... Read and Reread Again
The accuracy of proof and source documents is key to good genealogy work. With perhaps hundreds of letters, death and birth certificates, and other supporting documents to deal with, one risk is developing "tunnel vision" that leads to overlooking buried evidence of events beyond that originally sought from a particular document. Always look at your proof documents closely, and then reread them again for what you may have missed.
As a recent example, rereading a letter from the Historical Elmwood Cemetery in Detroit Michigan listing burials in an ancestor's large family plot revealed that a previously unnoticed baby was buried there. Xavier Rusch owned the plot but the baby was identified as Edwin Alter, a surname matching that of a married daughter of Rauch named Sophia. The baby lived only four months.
Once recognized, correcting this oversight required better research on the family of Frederick and Sophia (Rusch) Alter, the potential parents of this child. The date of death for the baby in 1909 suggested using the 1910 U.S. census - it lists the total births for each female in the family and the number still living. Sophia Alter was shown to be the mother of 2 with 1 child living. Known Alter family stories failed to mentioned this child who died young.
To avoid such mistakes, always read and reread your proof documents and look for the unexpected and any additional information they may provide. Use them for more than one purpose and avoid tunnel vision when looking at source documents. You can never tell what else may be hidden in them.