Hints and Tips

Remember that not all historical records have survived, and not all those that have will be included in any given online collection. Just because there's only one entry that looks like it fits doesn't mean it's the right one.
Be imaginative with spellings when searching indexes. People weren't always consistent in spelling their own names, and, especially if it's an unusual name, record-keepers or indexers might not have spelled it correctly. I've found Bushby Olliver indexed as Rushby, Bushley, and Buesley.
Also, remember to check familiar versions of names - Richard Williams was listed in the 1891 census as Dick, and his mother Jacintha was listed as Jessie in 1851.
Don't assume that a record is wrong. If someone has a different name, a different birth year and a different place of birth, chances are it's not the person you're looking for.
A year or so before the birth of the eldest child is a good place to start when looking for a marriage, but remember that one or more of the eldest children may have been born before their parents' marriage, or they may even be the children of a previous marriage. And, of course, the couple may never have married at all, even if they are listed as husband and wife in a document.

So don't assume that someone has died just because you can't find them in particular census - they might surprise you!