What i suggest would be:
to make notes on each of the values, and how they are transformed...pick 3-4 major themes(death, fate or self determination, etc) , find out the (b)value(/b) of the characters/context, and make 5 points on each of the texts for each of the Themes (each point; 3-4 lines). Focus on (b)what(/b) Stoppard has transformed in the theme explored in Hamlet and the same theme explored in Ros and Guil, and why he has? (different contexts hold different values).
And MEMORISE them all!
(and integrate quotes into your points so that you don't have to remember quotes seperately, and it elevates the level of sophistication of your answer)
Also make notes on Structure and language/ maybe characters also...
Goodluck!
Edit: You MUST know the value associated with each theme. Value is NOT a Theme. For example the valuse associated with Death is "the belief in Afterlife"