Identify the purpose of the show. Think of the dramatic genre: was it a drama, a comedy, a one-person monologue or a musical? This will help you decide what the play's essential intention was, which will figure heavily in your evaluation of it.
Judge the textual elements; in other words, the quality of the script. Was the dialogue riveting and authentic or flat and contrived? Did the humorous lines deliver laughs? Remember that even serious dramas often have a dose of comedic relief. Was the plot compelling enough to hold your interest?
Rate the quality of the characters. This is distinct from the quality of the actors. Did the characters have depth and genuineness? Were there too many (or not enough) characters in the ensemble? Were the characters theatrical cliches or did they make the play interesting and enjoyable?
Evaluate the actors. One unique feature of the stage is the immediacy of the performance. Theater is acted out live, and good actors with real stage presence can achieve a rapport or emotional connection with the audience. Did the actors adequately portray their roles or were they miscast?
Judge the visual elements of the play, including costume, set design and lighting. Such features enhance the visual appeal of a play. Was the set designed in a way conducive to the message of the play? Good scenery doesn't have to be elaborate; minimal design (such as that used in most productions of "Waiting for Godot") can be equally effective. Similarly, were the costumes well-made? Did they look authentic and suit the personalities of the characters? Did the lightning enhance your enjoyment of the play or was it too light, too dark or distracting?
Analyze the use of music. This has obvious importance for a musical, for which song and dance are the centerpiece of the show. Were the songs catchy, memorable and well-written? Did they strike an emotional chord? Was music used effectively as a narrative device to further the plot and action or did it seem out of place and contrived? Non-musicals sometimes use music as well, either as background or as "source music" (music that "exists" in the action of the play itself.)