You need to establish quite quickly whether your DOWs are of Scottish or English origin.
(There are also Lebanese, French and Chinese DOWs that I am aware of, no doubt there are others!)
The reason is that generally the Scottish records are kept quite separately in Edinburgh, 400 miles north of London where the English & Welsh records are located.
Hence the importance of establishing which country is involved.
There are similarities in the records kept in the two major locations; but there are differences.
One to be wary of is that Scottish Civil Birth Registrations (started about 1855) generally give the Time of Birth as well as the Date.
English & Welsh Civil Birth Registrations (started about 1837) normally do not give the Time, only the Date. In these, if the Time is present, it usually implies multiple births, eg Twins etc.
This difference can cause major misunderstandings when someone only acquainted with the E&W system, starts to research in Scotland.
Prior to these respective dates, most of the available information come from church records which for many reasons are incomplete.
Generally, the churches recorded Baptims/Christenings which could be from shortly after birth through several months to a few years later, some families being baptised in batches. (Cheaper by the dozen?)
So on those earlier records, take the date as a guide; but not an absolute guarantee of age etc.
Spellings of names vary enormously for various reasons.
You should collect together all you can within your family contacts, recording everything even if described as legend or probably fairy-tale. It is amazing how many of these can be unravelled to give clues.
Try to get back to around 1880, this tends to be a watershed; but earlier if possible.
On the Web, you should find the following free site of use- www.familysearch.org
Also you can get access to official records of those earlier records at two separate Web sites; but to use them fully, you will have to pay by Credit/Debit card.