Drink every time they get in an unsubtle use of the ‘tobacco and boys’ comment.
In fact, drink whenever a line is clearly using the Baines note as its source.
Drink every time he is referred to or refers to himself as one of his characters. Drink again if he quotes his own lines (or paraphrases for no apparent reason).
Drink every time ‘Ganymede’ is mentioned (this rule stands for his actual works too).
Drink every time one of the Toms is mentioned—Watson, Walsingham, Kyd, Nashe, etc—and finish your drink if this is turned into some kind of tom cat/Kit pun.
Drink whenever Shakespeare comes up in some overly casual way. Finish your drink if it is to call him a countryside yokel or an upstart.
On the flip side, if the thing is about Shakespeare and Marlowe is a side character, drink whenever Marlowe is in a scene or is implied to be a friendly rival to spur Will on and then die to get out of his way. Consume everything within reach if Kit is solely there to make flirtatious comments and talk about Hell.