Not sure about setting the pagesize being recommended by MS. Every MS course i've been on and it was covered its been suggested to leave it at OS determined for the vast majority of people.
As a general rule of thumb it should be 50% more than your memory, so, if you have 512meg then the page file should be max of 768. Overall though, most people don't need to touch the pagefile size, are you encountering problems that makes you think you need too?
In an ideal world you would have the pagefile on a seperate partition to your OS as correctly stated however, in my case I have stripped Raptors (10000rpm) for my OS so it makes sense to keep my pagefile here as well - they out perform the normal stripe (7500rpm) I have for data.
If you are on a single disk system then it probably wont make much diference as the disk heads are still fighting with each other but, if you have dual disk (or more) system then move the pagefile onto a non-OS disk -assuming your OS isn't on uber disks of course!
edit: ahh sorry, on the subject of size, Guido is correct. *IF* you really feel the urge to play with the page file, set the minimum and maximum the same size. But, unless you are getting errors (tell us what they are) then dont touch it and leave it as OS managed.