Signal Rule Scenario: From Clear to Approach

Your best bet is to wait until you get the job because each road has their own rules based on some set standards, aka rule books, but have been customized standards. CSX is based on NORAC, while railroads in the Chicago area use CORA, western roads signed up for GCOR which works different than NORAC, and Canadian railroads use CROR.

This site has some helpful information:

http://www.railroadsignals.us/rulebooks/rulebooks.htm

But I wouldn't worry too much about this stuff because you'll be given a classes and lessons with some quizzes and then ultimately an exam, which you need to pass in order to obtain your conductor's job, or whatever job you apply for. In the end studying and preparing for stuff now will only confuse you.