I passed my CCNA some years ago with flying colors. I would have suggested that you learn subnetting inside and out. Its not just about knowing it, its about being able to do it quickly. Too many exam questions indirectly rely on you being able to do it. I've been doing it for years, but even still I was worried I choke under pressure.
When you get to the exam, before the time starts, I wrote down my subnetting charts on the scratch paper they provide. It took less than five minutes and when I was done I started the exam for time. I constantly referred back to the chart and knew that those figures were correct. It was one less thing that I had to think about.
Hope that helps, I know it saved me.
Certifications: CREA, MCSE: Security, CCNA, Security+, other junk