For this Monday the first part of a test made for the Naval Academy Sailing Squadron in 2001. It is therefore a little old, but you can still get some practice from it: NASS rules Test 2001 part I-III.pdf
Half the skill you need as an IJ is to be able to answer questions you've never heard before. And sometimes the question asked is not specific enough, and needs to be reformulated before it can be answered. What is the expression: "Think outside the box?". If you don't know what the answer could be, translate the question to the current rule-book and try to answer that. And as always, please don't hesitate to comment or let me know what your solutions are.
If you have the time you can also have a look at the website of the NASS. True to there nature, you can find - with a little digging - a lot of information about procedures, safety and boat handling.