It is important to study effectively for the L1 exam. Remember that the L1 exam is just the first step into the judge program and isn't intended to be too gruelling.
The IPG isn't part of the L1 test at all. The L1 test only uses the JAR (Judging at Regualar REL) for it's questions where the players have done something wrong.
When studying the CR (Comprehensive Rules) focus on just the following topics:
- Parts of the turn and the things that happen in each of them
- How spells and abilities are played
- How they resolve
- How the layers interact
- What Two-Headed Giant is (really just read the 2HG FAQ).
A couple of quick skims of the MTR are likely to be enough for the few questions that might be based on it. There will be a few things in there that might surprise you, those are the bits to remember.
Most usefully log onto the Judge Center (judge.wizards.com) and do some practice tests. Easy Practice tests are a good gauge of how hard the L1 test is and the fully explained answers will help you understand what you didn't understand.
The other thing that must be done is you need to judge a few events, preferably with the Level 2 judge that will be testing you. Judging a couple of events is required before you can be certified as a Level 1 judge. Remember you don't need to be certified to judge events.