Analyzing malware, or malicious software, is more of an art than a technique. Because of the wide nature of these products, there are limitless ways to hide functionality.
Some common tools for malware analysis include simple programs like strings. More complex analysis can be conducted by looking at the headers of executables with programs like PEiD and PeExplorer. Finally, the most complete analysis can be done with debuggers like IdaPro and OllyDbg.