Brick Walls and the Census
So you can't find that elusive ancestor. You know his/her name and the spelling so that's not the problem. But if you're looking for that ancestor by his/her name, you may be making a mistake. It was very common for names to be misspelled, especially if the census person did not speak the same language. Then the transcriber might've made another mistake with that name that was misspelled to start with. Omit their first or middle names when searching; instead search by location and dates and perhaps surname. Or skip the surname and search first and/or middle. If you can't find anything and you've tried everything you can think of, it might be time to browse the whole record collection.