I did not even know there was a Google Analytics certification a week ago. When I stumbled across the designation I said "I should get me one of those." I've been using GA for years and figured a certification was within my grasp. It took me about 8 hours of study and $50, but I got it done.
OK, this is more the story of how I passed the test than an authoritative guide, but I hope it helps. I did the most logical thing first, I Googled "Study Guide for GAIQ." I found some great advice, but I think this post did the best job:
Everyone who has taken the test says to watch all the videos provided by Google in Conversion University and I concur. I usually hate watching videos for training because they tend to suit the slowest learners. I like to read, skim and hone in on things I don't already know. These videos are well done though. They are really more like slide shows with a few videos dispersed throughout. They go quickly so I paused and re-watched a few slides that I needed to study more.
I had a second laptop setup as suggested, but I found it was easier to open a second browser than to change computers. Note: You need a second browser not a second window in your browser. I used Chrome for the test and Firefox to look up answers I was unsure about.
One thing I did not like about the test were all of the questions that were not in the study materials. A few I could not find even after Googling for answers and scouring the GA help section. I took my best guess on those.
I did learn some new things by going through all of the training materials. Definitely worth the effort. If you are a regular user of GA, I recommend getting this certification. Good luck!