I've used a macbook since 2006, and it's my ONLY computer. Just so you know my experience level and such.
Since it's a powerbook, you most likely want to install an earlier version of Leopard. Definitely not Snow Leopard. If you can post the specs of the laptop, that would help. That way I can tell you if you should install Tiger or Leopard. We don't want a slow laptop now :).
The first thing you should do when you get the computer is max out the ram capacity, and you can find the capacity online. Pretty self-explanatory.
Safari: I highly recommend using Firefox, in any version. The reason Safari is the "fastest" is because it's barebones. Safari would work fine, but honestly, Firefox is so much better. And I'm pretty sure there are more Add-ons and themes and stuff for Firefox.