We’ve worked back through John’s life to the very first moment: his birth.
I already know from his death certificate his birth date, and from his marriage record his birthplace. But for completeness, I now search for his birth record. In addition to good genealogy and sourcing practice, it’s possible that the birth record will have contradictory information from the marriage or death records that needs to be sorted out.
As before, if you aren’t already familiar with sources of birth records either to request as an eligible relative/researcher or to search what is publicly available, you can start by searching for “birth records <city, state, or country>”.
Instead of Ancestry, this time I’m on FamilySearch (an excellent free resource) in the “Michigan Births and Christenings, 1775-1995” database. My search is:

Even though this is accurate to what I’ve found in other records, the search returns no results! When this happens, it’s best to remove some information to increase the chance your search will return something. I like to start with location. Instead of Bridgeport, I will enter Saginaw (the county in which Bridgeport resides). The record I’m looking for is now the first result:

If this doesn’t work, try removing or using soundex or partial search for the last name, or giving a range to the year. Slowly expand your search to give you more results to sort through. As always, be careful for duplicate names and find some corroborating information. Sometimes this all fails, and if you have the patience you can find the record by going through scanned images page by page.
While the birth record does not give me any additional information, it does support the information I’ve already found through other sources and is a good cross check and record to add to my record of John.