Using the census as one of the many tools for your genealogy research is a smart choice. It is also one of the most popular choices out there for those who wish to search from the convenience of their own home and personal computer. However, one must be careful while using this tool, to remember that although an excellent source, it can still be full of many mistakes. Such as birth dates that are off by a year or more, and misspelled names.
When you think of a census taker going to many different doors and speaking to many different dialects it is easy to see how a year or a name may be written down incorrectly. Especially since the people being questioned most likely didn't read or write and probably could not spell their own names for them. For example take the German surname Wiese. This name alone can be pronounced many different ways, WEE-ZZ, We-ss, Witz, and Wise just to name a few. Now also keep in mind that the name could also be spelled the way it sounded. Such as Wise. The letters could be changed around as in Weise, Weiss, Wiess or Wiese.
Same thing goes with a forename, say you have Louise Wiese, you know she was your great aunt. Yet in the 1870 census it names, Joachim Wiese, and his children James, Emma, Aggie, and Louis.
Louis? You did not know there was another son. But, wait, use caution! You know there is a Louise, and she should be listed in this census, but instead Louis is. It is entirely possible that the "e" was left off the name altogether, or it could be another child. This may take a little more research to be sure Louise is Louis. You can of course use the birth date listed as a guideline in your decision making if you have it. You can also of course go further, and look to see if you can find Louis in any other census records. In this case use caution in making your choice. I would consider this a mistake from the census taker, and say it was Louise myself, but, I would make a note of it and keep this in the back of my mind while researching until I found satisfactory proof.
Use caution with the dates listed. For instance, you have just found great grandma Cecily in a census record for 1880. You are so very excited to have found her because now you have the names of her parents and several of her siblings. Yet, you are slightly confused because her birth date differs from the one you have seen before. This is all to common and happens to many people out there searching the census records. You just have to know not to take the dates you see as hard evidence that great grandmother was born in 1878 when her tombstone says 1877. Either could be wrong. However, you have something to go by, use this as part of your research until you have the actual documentation for the date. Make a note of the inaccuracy of the dates with your ancestor in the notes section, this way if you share your tree that person will be aware of the inaccuracies as well.
The best way to determine a birth date is an actual birth certificate or baptismal record. Use the what you find in a census as a guide only. It can be very helpful for you to to keep a file on each person you are researching. I keep a cover page on each one. It has a list for each thing I need to have on a person such as, census records for years alive, birth certificate, baptismal record, marriage record, death record and obituary. I check each off as I find them, and place the record in the file. This way I can easily pull a record on a person in question.
I cannot stress enough to use the census as a GUIDELINE to your research. Take notes! From the birth place listed as being several different places in various census, to the dates and name differences as well. These little notes make a huge difference later when you need to go back to this person, or you are questioned as to how you found this information.
That being said, the census is still one of the best sources for the armchair genealogist. Good luck and happy hunting!