Back in the day, my lab partner and I got first place in the lab competition and actually went to the national level. That being said, we didn't study at all, and if we had, I seriously doubt it would have helped. The experiments are usually pretty cleverly designed. We won based on completely random facts that I had absorbed from my chemistry book, coupled with an educated guess on our parts. That's sort of the way that I found the entire chemistry olympiad set up--if you could remember random factoids, you were better off. Read through the elements section of the CRC if you're doing the periodic table competition; other than that, I have no advice on studying. Good luck.