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The knowledge tests have lots of questions of METARs and TAFs and rather than copy this information into every question, I’ve posted it here.
AVIATION ROUTINE WEATHER REPORT (METAR)
Handbook of Aeronautical Knowledge p 11-4, 11-5, 11-6
An aviation routine weather report, or METAR, is an observation of current surface weather reported in a standard international format. While [...]

The Knowldedge Tests have lots of questions on the compass, especially turning errors. The Handbook of Aeronautical Knowledge covers the questions well so I’ve quoted it here with bold for things to remember. Items in brackets [...] is added.
Variation

Although the magnetic field of the Earth lies roughly north and south, the Earth’s magnetic poles do [...]

The FAA publishes the questions for the knowledge tests but not the answers. The FAA takes the questions verbatim from the FARs and its own publications. Each question has a code number that indicates where the answer to the question can be found. By searching the appropriate document you can be certain of the answer [...]

Revision: 2009-01-11
The NTSB has revised the reporting requirements. Details are here. Two changes affect Part 91 airplane operators. Reports must be made if a failure of the Electronic Flight Instruments occurs or and if a portion of a propeller is released while in flight.
The National Transportation Safety Board is an independent U.S. Federal agency that [...]

These regulations come up several times in the written tests and are worth memorizing.
§ 91.3 Responsibility and authority of the pilot in command.
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
(b) In an in-flight emergency requiring immediate action, [...]