Sometimes you are searching for someone with a complicated or easily-misunderstood surname, he can be really hard to find. His surname can be spelled so many different ways.
For example, last night I was searching in the census records at Ancestry.com for an Ezra Lorenz whom I knew had lived in Durham, Kansas. My only result was an Edward Lawrence from New Jersey. I tried different spellings of Lorenz. I tried his wife Sara Lorenz, which didn't help either. I tried his son Clarence - no luck.
But this morning I tried my last-ditch strategy: I searched for all the first names that I knew in the family without the surname because first names are less-likely to be garbled. My search parameters were
First Name - Ezra
Born - 1884
Spouse - Sara
Child - Alvina
Child - Clarence
Child - Pearl
Child - Vernedda
Location - Marion County, Kansas
And immediately the results popped up with all their census records. When I looked at the 1920 census, I saw why my original search didn't work - the handwriting was very sloppy, and he had been indexed as "Ozra Leonz." His wife was indexed as "Kate" and the children as "Athena," "Clarence," "Pearly," and "Beatric." Somehow these were close enough for the Ancestry search engine to find the family.
I think this works because first names are more likely to be correctly transcribed and because there were no other clusters of identical first names. I found my grandfather on a very messy page of the 1921 Canadian census this way when I had given up all hope of finding him.
If you're having no luck finding a family, try searching just on all the first names you know and a location.