If you have an ancestor with an unusual last name, you might try searching the census using the last name only (and don't forget to use "wild cards" in your spelling options), especially if you can narrow down the likely geographic area. That will reduce the "noise" that possible misspellings of first names creates, and it may uncover some other family members living in the same region.
In a like vein, you might try some name-less searches. Search using only the place of birth of your ancestor (again focused on a particular census region). That can reveal friends and neighbors from the same home country. Once you have those names, you can look at their census pages (as well as a couple before and after them) and you may find your ancestor. This is sometimes fruitful if the census taker did "bad" things to your ancestor's name when it was recorded. Remember, during immigration, friends and neighbors and family often traveled together to this country and then ended up living in the same area.