First things first. As one of my friends would say, "I want more meat!"
Your introduction is highly waffly until the very last line, which is where you finally get around to saying the good stuff. Even then, you may wish to consider recouching this in slightly more sohpisticated language. Remember that an introduction should state all the texts you're going to look at (for HSC level, anyway) and to give an outline as to how you're going to answer the question. You must answer the question! If it's easier, you may re-word the essay question into your introduction (to better formulate an answer) however this is generally frowned upon if you're hoping for high high marks. If not, then go ahead and do whatever it takes to make it easier
Paragraph 1: I should probably state here that I'm analysing this from a first-year Uni level essay-writing perspective. I'm remembering now how much generic "stuff" tends to be shoved into essays, however even if you do this (and I guess we do need to do this for Eng Adv, all hail EE1) I strongly advise you ensure that each paragraph ANSWERS THE QUESTION. For basic starters, something I *still* do is to have a somewhat blunt draft opening sentence to get my mind around what I'm going to say. If what you *want* to say is "One of the differences between Hamlet and R&G is the historical context. By reading two different takes on the same story written at the same time, one is made aware of the dominant attitudes during that time and how they influence the text's dominant reading", then say that - but in better words.
You really have to remember that you are here to answer the question. There is a lot of "stuff" to cram in, but use this "stuff" to support what you're actually saying to support your theory. If you just put it in, it makes me wonder whether I'm reading "A Random Review of Techniques Used in Blah Blah Blah" or an english essay.
Paragraph 2: I'm slightly concerned about the sexual connotations references. There are *lots* of bawdy jokes in Shakespeare, so the validity of your point may be questionable. But it's worth saying if you explore it from another angle... read the scripts over again, and you'll find something to explore your sexual revolution theory. *That* is something you can expand upon.
Paragraph 3: Good! But bring it back to the essay question. ALWAYS answer the question! I used to get in so much trouble for this. My teacher reminded us how easy it is to go off on tangents when you're writing an essay. Sure, the ideas might flow, but the ideas may not sufficiently obviously answer the question. If you have to re-write the essay question next to your page to remind yourself of what you're supposed to be answering, then do.
Paragraphs 4 and 5 are sort of there and sort of not - again, they need to directly answer the question. I would also like to see more flow, which is generally lacking a far bit overall through the entire essay.
Paragrapph 6 is silly on its lonesome with no clear indication of it's purpose. Remember - answer the question! Make it clear that you're answering a question!
Paragraph 7: Don't leave the meat at the bottom. State very clearly what you're going to argue at the BEGINNING of the paragraph!
Conclusion: Avoid one-sentence paragraphs like the plague. Also, more "meat" required.
On a general note, you're missing some pretty important bits of "stuff", as well as terminology (techniques). I see absolutely no mention of "humanism" and "existentialism", and they really should be. Your second-last paragaph has so much potential, but I think you rushed over it - a pity, as it covered some very important issues which require more than glossing over.
In regards to flow, a lot of what you say does not follow on from the previous paragaph... for example, "Democratic governments and constitutional monarchies brought about changed attitudes towards the monarchy during the 1960s. There was more awareness of the common man that represented all classes and not just the nobility. Stoppard reflects this value in his play by transforming the subject matter from Hamlet to Ros+Guil, symbols of the everyman. We therefore witness a value of the common man. "
Could be rephrased as "The democratic governments and constitutional monarchies during the 1960’s brought about changed attitudes, including a shift of focus from the nobility and a raised awareness of ‘the common man’. Stoppard conveys this contemporary value in Rosencrantz and Guildenstern by changing…" etc etc.
Will leave the criticism there for today. As a mark, I'd expect about 12/20. Remember, that means you have 8/20% room for improvement!