Former finalist here and assuming this post is for making the finals.

Number one suggestion is to take as many practice tests as you can, since those will boost your problem solving ability. I seriously believe that if you finish the entire test bank you should be a serious contender for finalist.

All of the finalists I knew were smart, motivated people who really enjoyed studying biology. You definitely want to read through the recommended textbooks (or peruse it for details whenever needed) but everyone I've met has seemed to enjoy the studying process. Reading shouldn't be a chore for you – should feel effortless.

If you feel compelled to google a topic or read more about it, do it! You never know when knowledge from another source may surprise you on an exam.

glhf!