What is the difference between session laws and codes, and which publication should I use to find the current law in a particular jurisdiction?
Session laws are laws that have been enacted during a legislative session. Session law publications publish these laws in chronological order, by the legislative session in which they were enacted. A session law may be subsequently amended or repealed by a later session law. Codes (sometimes called statutory compilations) publish the laws by topic or subject, rather than chronologically. In addition, codes are periodically updated with supplements or new editions in order to reflect changes (e.g. addition of new laws, changes in existing laws, or deletion of repealed laws). If you are looking for the current law on a particular topic for a particular jurisdiction, you should consult the code for your jurisdiction because the laws are arranged by topic and are updated to reflect any changes in the law. If you need to find the text of a specific law as it appeared when it was originally enacted (e.g., Civil Rights Act of 1964, as it looked like in 1964) then you need to consult the session law publication for the appropriate jurisdiction.
Where can I get the text of a law that was very recently enacted (within the last year or sooner)?
One of the easiest sources from which to obtain recently enacted laws is a legislature's web site, e.g., Congress.gov (for federal laws) or through a commercial vendor's web site, e.g. Bloomberg Law, Lexis Advance, LexisNexis Academic, and Westlaw. The first print source you are likely to find session laws in are advance legislative services. These are usually published by the commercial publisher of the annotated code or statutes for a particular jurisdiction. Print sources for recent Federal laws (Public Laws) include the United States Code Congressional and Administrative News (USCCAN) and the advance legislative pamphlets that accompany the two annotated U.S. Code sets, U.S.C.A. and U.S.C.S.
I have found the law (code section) I was looking for; now what sources should I check to make sure there haven't been any changes in the law since it was published in the code volume I read it in?
In print, the first step is to check any supplements that accompany the code volume. The supplements are usually in the form of a pocket part inserted in the back of each volume. In some cases a pamphlet supplement may be published instead of a pocket part and shelved near the volume.
The second step is to check to see if an advance legislative service is available for your code or statutes set. These are usually soft-bound pamphlet volumes published by the publisher of the annotated code for your jurisdiction. They are usually shelved at the end of the annotated code set. These advance legislative services publish the text of laws enacted during the current or most recently concluded legislative session. They usually contain a table at the back of the pamphlet to help you determine whether your code or statute section has been affected by any recently enacted session law(s).
For example, United States Code Service, published by LexisNexis, has an accompanying advance legislative service, Advance pamphlets to the United States Code Service. The Advance pamphlets are published monthly and generally publish new federal session laws within a month or so from enactment. "Statutes Amended, New or Repealed". This table can be used to determine if a given statute has been affected by a recently enacted session law. If the statute is listed in the table, the effect (amended, repealed etc.) is indicated along with the session law citation.
Online versions, whether obtained through a commercial service or through a reputable free source like http://uscode.house.gov/, tend to be the easiest way to view the current version of the law; here, there is no need to consult a pocket part or supplement, because changes are reflected in the text with little lag time.