If you can’t find someone in a particular English census, do a search for the address at which they were living ten years earlier or ten years later. If you don’t find them immediately, look along the whole street and in streets nearby as houses were occasionally renumbered; also landlords sometimes moved tenants (which the majority of people were) to a smaller or larger property as their family size changed. This method will help to work around indexing errors.
You might not have found the person you seek because they changed their surname. For an example look at the 1891 census for Stratton in north-east Cornwall. You should find Alfred Badcock, his wife Lydia, four children and a domestic servant living at 4 Fore Street, his occupation recorded as cordwainer [RG12/1797/14/2]. In 1901 they are living a short walk away in Bridge Street [RG13/2175/11/13] but their surname is now Saunders. The names of the eldest children make it obvious that it’s the same family; Alfred is recorded as a bootmaker and shopkeeper.
If you still can’t find the person or family you are looking for (but have found them in another census year), look at a census in which you have found them and look at the neighbouring families. If you can find the same family in the queried year they might be living near the family you seek.
There are plenty of inaccurate transcriptions in the indexes available to us, so be creative about the name variants you enter and think about the kind of error (‘Miller’ instead of ‘Millen’, for example) that might have been made.
If a member of the family you are seeking has a distinctive forename, search by forename and omit the surname. Some indexes are also searchable by occupation.