1.Since students do not see any slides in the long essays the appropriate choice of these works in relation to the question is critical to a successful argument. I would advise students to clearly decipher the multiple tasks being addressed in the stem of the question and select two appropriate works to include in the discussion. One needs to get a lot of "mileage" out of the two examples, so students need to think hard and devise a plan quickly to form an argument -- keeping in mind not to force a square peg into a round hole.
2.Moreover, advise students to follow the specific written directions. In one of the long essays students must choose at least one work outside of the European tradition -- you would not believe how many students decide to ignore this direction. In the other long essay, a specific direction might include selecting a pair of works of art, before and after a certain date. An incorrect or inappropriate choice will serious hinder the argument and thus the score on the essay. (Incidentally, good students naturally compare and contrast the two works seamlessly in their essays. But, students do not have to compare and contrast the two works if it is not part of the specific written directive).
3. Fully Identify -- Not all works of art can be fully identified according to: name of artist, date, title, medium, size, location, etc. As a result, advise students to identified the examples as specific as possible to let the readers know clearly which works of art are being addressed in the essay. For example, identifying an example as "a Buddha figure" is simply inappropriate, while identifying the same example as "14th century Central Tibetan Seated Buddha" is getting much closer to the expectations of "fully-identify."
4. Dates -- I personally shy away from telling my students to know exact dates. Instead, we work with larger chunks of 50 to 100 years and practice matching them to stylistic periods and epoch. Frankly, some students need help just knowing that year 1430 is 15th century.
5. Guessing on the MC -- To answer your question: No penalty for leaving a response BLANK -- no response. But, one-third of the number of questions answered incorrectly will be subtracted from the number of questions answered correctly. It is IMPROVABLE that mere and random guessing will improve the score significantly. On the other hand, since there are only four possible choices ..."if you have some knowledge of the question and are able to eliminate one or more of the answer choices as wrong, your chances of selecting the correct answer is improved, and it may be to your advantage to answer such a question." (2004 Released exam, page 19).