The first division in your analysis is internal vs. external distinction; in other words, are you going to examine the details of rhythm, harmony, instrumentation, etc. inside a musical “kind” or “type" (take, for example blues), or are you going to examine the details of your musical selection compared to other genres (for example, are you going to compare and contrast jazz to Western orchestra music, or are you going to compare Coltrane to MJQ?).  This broad distinction then allows you to focus your examination on narrower similarities and differences:  instrumentation (saxophone vs. vibraphone), rhythm (4/4 beat or 5/4 beat), location on the historical timeline (early foundation vs. late variation) etc. Anaysis consists of taking a piece apart to make valuable observations about its parts – to show “how” a piece of music “works.”  In a fairly long analysis, virtually all of the musical elements should be discussed.  If you are examining one piece inside a canon, you might  discuss the finer elements, getting closer and closer to what distinguishes your sample from others in the same general field.  What makes an Arnold Schoenberg piece different from, say, a Mozart piece – that’s a large distinction that can be dealt with in large strokes, but the difference between Coltrane’s “Dedicated to you” and his version of  “My One and Only Love” involves close looks at phrasing, improvisation moments, even lip techniques.