Before you start browsing the census or look up names on the few areas that are indexed, it is best to learn more about the 1940 enumeration. The location of households is shown, being street, avenue or road, etc. as well as house numbers in cities and towns. This is followed by household information, such as the number of the household in the visitation; home owned (0) or rented (R) an the value of the home. If renting, the monthly rental fee will be shown.
People who were in their usual place of residence on 1 April 1940 were listed. If they were temporarily absent, "Ab" was written after their names. One of the best features is the X after the name of the person providing the information. However, I have seen some sheets where the enumerator failed to mark this information. Relationships to the head of the household are shown as well as personal descriptions. Martial status, age at last birthday, color or race and sex are denoted.
Education questions were asked. Did they attend school or college any time since 1 March 1940 and the highest grade of school completed.
Birth locations were to be by state, territory or possession. Foreign countries were shown for births in that location as of 1 January 1937. Canadian births were reported as Canada-French or Canada-English. The Irish received classifications of Irish Free State (Erie) and Northern Ireland. Foreigners had to report their citizenship status.
A very helpful area for the genealogist is the residence as of 1 April 1935. Their residence as of that date is shown. If they were in the location of the 1940 Federal Census "Same house" was written in the space. City or town, county and state were listed for those in different locations.
Individuals who were 14 years of age or older had to provide employment information. They were asked if they were at work for pay or profit in private or nonemergency government work during the week of March 24-30. If not, were they at work on or assigned to public emergency work? This included the WPA, CCC, and WPA, and was for the week of March 24-30. Were they seeking work? Information was included on whether they were engaged in home housework. The number of hours worked was shown for the week of March 24-30, along with duration of unemployment up to 30 March 1940. Occupations were shown, such as salesman, teacher, physician. The number of weeks worked in 1939 was shown and their monthly income for the 12 months of 1939 ending on 31 December 1939.
People whose names happened to fall on lines 14 and 29 had supplementary questions noted. The place of birth of father and mother was shown and the mother tongue. Veterans information was collected and people on those lines were asked if they had a Social Security number, as well as deductions. Their occupation was shown and women were asked if they had been married more than once, age at first marriage and the number of children born excluding stillbirths.
This is a tedious census to work through. Further information can be found at the National Archives web page http://www.archives.gov/research/census/1940/general-info.html#questions.
The indexing of the 1940 Federal Census is progressing because of dedicated volunteers. To work around the lack of indexing you will need to use the Unified 1940 Census ED Finder http://stevemorse.org/census/unified.html. It is helpful if you know the enumeration district from the 1930 Federal Census.
As with any census, there are surprises on the 1940 Federal Census. I have found people where least expected and with information that surprised me. Comparing it with the first enumeration in 1790, the advancements in record taking are startling. Even so, you will find some "hen-scratch" handwriting!