XP Ubuntu dual-boot, which one first?

Nothing too earth-shattering here, just wanted to make sure I do this right. I have a ~3 year-old machine that has been moving painfully slow for quite some time, so I figured it was time to try something new. I am about to reformat my hard drive and install XP Prof. and Ubuntu. I was hoping I could get some advice on the best way to go about doing this. I know a decent amount about computers, including when I could stand some guidance through the process. I have my boot disk ready to reformat, the Ubuntu CD burned, and my Windows CD w/ serial ready to go.

First off, it's been a loooong time since I've partitioned a hard drive. What are the best practices for doing that?
Second, should I install Windows first, or should I install Ubuntu first, or does it even matter?

Any help in this matter would be greatly appreciated.

Thanks!
-VZ