The 1930 US census became available to the public in April 2002. The
National Archives has information about it at
www.nara.gov/genealogy/1930cen.html
Megan Smolenyak's article
Locating Ancestors in the 1930 Census is a good overview of the challenges involved.
The National Archives has an extensive tutorial about the census at 1930census.archives.gov.
The 1930 Census is mostly not indexed by name. If your ancestors lived in a large city, you'll
have to find their address and Enumeration District.
You can read a list of the circa 1930 city directories available at the National Archives at
www.nara.gov/genealogy/citydirs.html.
The Family History Library (locally, in Greentree) may have city directories on microfilm
for you to borrow.
Stephen Morse's page Obtaining EDs for the
1930 Census in One Step (Large Cities) may be of help to you in locating enumeration
districts.
The page
Census Data for the year 1930 summarizes some of the data collected in the census.