Many test-takers find Passage 1/Passage 2 comparison questions to be among the most difficult on the SAT. Keeping track of multiple arguments and points of view can be challenging, and for this reason it is very much to your advantage to break the process into manageable chunks.

The single most important thing you can with Passage 1/Passage 2 comparisons is to treat them like single passages for as long as possible. That means:
1) Read Passage 1
2) Write the tone and main point
3) Answer Passage 1 questions
Then, when you’re done:
1) Read Passage 2
2) Write the tone, main point, and the relationship to Passage 1
3) Answer Passage 2 questions
And finally, when you’re done with Passage 2, answer the questions that ask about both passages (if they appear before questions asking about only one of the passages, skip them and come back later). Make sure you reiterate the relationship between the two passages before you begin the comparison questions. 
While long Passage 1/Passage will always have questions asking about the two passages individually, short Passage 1/Passage 2 may not.
The first thing you should do when you encounter short Passage 1/Passage 2 is therefore to skim through the questions and see whether there are any that deal with only one passage. If there are, read that passage first.