This answer is from personal experience. Just a quick word, the National Archive Branches all have different holdings. Their holdings are mostly regional. For example, the one located near me in Fort Worth, Texas houses indian records for the 5 civilized indian tribes among many other things.
They all carry all years of the U.S. Census and you must view them on microfilm. They are not digitized like or fully indexed like the ones at ancestry.com and heritagequest. If you are going to look up the census, you will have to do it the old school way where you first pull the soundex and then the actual census rolls. There is not very much on computer because they specialize in archiving the original documents. Their volunteers are very helpful there.
Whichever branch of the National Archives you are visiting, you might want to check into what their holdings are before you go. Here is a link to the nara webpage where you can get such info. Good luck and I hope you find what you are looking for.
http://www.archives.gov/locations/
For birth and death certificates, your best bet is not the National Archives, but the county in which the birth or death occured. If this is not an option, you might want to check into the catalog at the Church of Latter Day Saints. They have an extensive collection of birth and death registers for many cities, counties, states, and countries. Keep in mind that if you are looking for anything recent, privacy laws do apply.
Also, never underestimate the resources available in the local genealogy department of your local library. Usually, that is the best place to start since church records, newspapers, city directories, local genealogies, and genealogical publications for the immediate area are almost always found there.