It depends on your goal. Why do you want to analyze the piece? Just to analyze it? What do you want to learn?
You can study
- how he uses harmonic progressions, when are they conventional, unconventional, where is he modulating, where is he using typical chord progressions in a key, why does he employ a certain progression or modulation here, what emotional effect does this create, harmonic rhythm etc etc
- how he does voice leading, what rules he follows, what rules he breaks, when he employs it, when he doesnt employ it
- the structure/form of the piece, which part serve as exposition, which parts serve as development, where are the climaxes, where is the biggest climax, where are the low points, where are things static, where are things clearly moving in some direction, where are the structural commas, periods etc as it were, how are these things employed to give the piece emotional impact?
- how the composer employs melody and motifs, which motivic cells are present, how are they used to generate the material in the piece
and much more.