Read BBO's post above, 1.5 times is a good metric to go with, as it's a 'safe' figure. However, if you're using "Fast User Switching" in Windows, you may want to make ths bigger, as the pagefile is used for storing sessions.
Then, simply keep your pagefile away from your boot and system disks. It makes very little difference if it's on another disk that's written to/read from frequently - as the idea is that you rarely touch your page file (if you've got adequate RAM for the tasks you're performing, that is).
In addition, NTFS partition with a 4kb cluster is the 'best' solution for a pagefile partition (and I would suggest giving it it's own partition if you plan to use a different cluster size for everything else... if you are using 4kb universally, then you can bung it on a low-ish-traffic disk). You also want to set the min and max sizes for the page file to the same size, just for simplicity's sake. Of course, the best choice is an altogether separate disk/array for the pagefile itself.
Finally, out of the RAID-0 and non-RAID-0 choice... put the pagefile on the RAID-0, you'll get better performance out of it. Never, ever, put your pagefile in any array that has error correction (RAID-1 mirroring is also a culprit here).