I haven't taken the exam, so I can't offer advice per se. I've spoken with several people who have taken (and passed) the FYLSX, however, and this is what I've been told:
It's tough, maybe tougher than the bar exam. It's not as long and doesn't cover as many subjects as the bar, but the level of difficulty (I've been told) is perhaps harder.
Study hard, take lots of practice tests, then really take the time to compare your answers to the model answers. Not just a cursory comparison, but in-depth. Like the bar itself, I imagine that you will start to see patterns in the model answers the more you study and you'll get a feel for what they're looking for.
Check the CA bar website, they might have past exams available.
Successful test taking is a learnable skill, and involves more than memorizing the subject matter. If the FYLSX is like the bar, you've got to remember that the graders will probably not spend too much time on your test. Organizing your answer as clearly and logically as possible will get you the most bang for your buck.
Good luck!