A birth records search may be done in many different locations and sources. So here's help on where to look for such information.
In some cases that means a birth records search through the church records of the church your ancestor attended. You may have to hunt for those. Old churches have closed, and their records moved to the denomination's archives which are housed somewhere. Finding them can be a challenge both as to the physical location, and then the specific records. Most old church records have not been indexed, so there is a lot of thumbing through old birth registration pages involved here.
At a point in time as countries grew, the government began to require the registration of all births. It varies greatly from place to place, state to state, province to province, and even county to county. So you face more birth date searches as to where the records were required (which governmental authority), and where those records are now stored.
You may need to find some county or township records, or you may be able to find state- or province-wide records which are indexed, and point to the exact location to find your ancestor's birth data.
Sometimes there are no existing governmental or church archive records for your ancestor's birth. But, you may have an old family bible in the hands of some member of your extended family which contains the vital records of the family - the births, marriages, and deaths, at least dates.
Before you rely heavily on these records, read the page on family bibles. Not all the information may be accurate, for a variety of reasons.
Before radio and television, not to mention the Internet, people got much of their news from local newspapers, most often weeklies. Many of these papers published for a short period of time, folded, and then were replaced by a new newspaper. In many areas, these old newspapers, at least the copies that were left, were gathered up by universities and archives and libraries, and microfilmed for posterity. Your birth records search may find birth announcements for your ancestors in such archives.
My mother and her father about 1912 when she was 4 years old