Sometimes we need to just stop and ask why we are doing what we do. I'm not starting a whole philosophical debate on the Meaning of Life, I just mean that as genealogists we should consider why we are performing a particular search. Suppose that you are searching for an ancestor's birth certificate; fine, that's a very sensible thing to do. But why do you want it? Is it because you like the nice wavy pattern on the watermarked paper, and the offiicial goverenment stamp at the bottom (I'm talking about England and Wales here, by the way)? No, it's because you want the information it contains. So it's good if you find the birth certificate, but it need not be a disaster if you don't, because you might be able to get the information you want from another reliable source.
Back in the Middle Ages, when there were hardly any census name indexes, I was trying to find a family in the 1861 census in Glasgow. The only way to do that at the time was to hope they were at an address from a certificate, a will, directory entry or some other source close to the census date. I wanted to find out about my great-great grandparents, starting with their ages and birthplaces. I had found their marriage in 1849, but this was in Scotland before the start of civil registration in 1855 so all the information I got from that was the date and place. I tried the address on the birth certificate of one of their daughters born in October 1861, but the weren't there. There was an older daughter born in 1858, but they weren't at that address either. Then I found the death of a child in December 1860 at yet another address, but they weren't at that one either.
At this point I gave up on this line for a while. If they had lived somewhere smaller I might have searched the whole place, but this was Glasgow, so it would have taken a very long time. I decided it was more sensible to work on another line instead, and then I made a breakthrough. It was the best kind of discovery, one that you make by accident when you are looking for something else altogether. I was looking at Poor Law applications in the Mitchell Library in Glasgow for my elusive Collins ancestors when I spotted an entry for Margaret Charlton. This was my great-grandmother's maiden name, and it was cross-referenced with the surname Soutar. Charlton is not a very common name in Scotland, and the application was dated July 1861, so this had to be her. And so it proved to be.
It hadn't occurred to me to look for the family in the Poor Law records, but the single page document that I saw gave me all the information I would have found in the census, and more. Not only did it provide the birthplaces of the whole family, but for Margaret and her four children the actual street addresses were listed. Better yet, it showed that William had been in the army for 15 years, and had been discharged about twelve years earlier. This was all news to me, and I now I had all kinds of leads to follow up. When I did eventually find the family in the 1861 census, after it had been indexed, it was a bit of an anti-climax. It was nice to have, though, and it provided me with yet another address for them, making four different ones between December 1860 and October 1861.
So it can pay to think laterally. Getting a birth certificate is the obvious way to find the mother's maiden name, but if you can't find it, or if your ancestor was born before the start of civil registration and therefore has no birth certificate, the birth of a younger brother or sister will provide the information. Of course, you have to be sure that they are full siblings, and not half-siblings.
There are all kinds of places where you might find vital information on dates, places and relationships, not just in registers and certificates. My poor law application is just one example, but it illustrates the fact that your ancestors might have had to provide details of their birth and marriage, and perhaps even prove it by producing written evidence. Schools, employers, the armed forces and all kinds of public authorities might have required this at some point, so don't give up when the head-on approach doesn't deliver the goods.