Assuming all drives are of about equal performance, the best place for the pagefile is:
On the most-used partition of your least-used hard drive.
"Least-used hard drive" because that drive will be less busy with other things.
"On the most-used partition" because that's where the heads will be much of the time already. (On an SSD, this doesn't matter.)
If you only have one hard drive, just put it in the most-used partition on that drive. (Or if it's an SSD, just put it anywhere.)
If you have just one partition on one hard drive, just put it in that partition. :)
As others have stated, performance gains will likely be slight if noticeable at all, unless you're hitting the pagefile a LOT. Most systems are not.
There is an argument for putting the pagefile on a partition of its own: You can then use PerfMon or Resource Monitor to monitor the activity on that partition or disk, and thereby find out how much you're hitting your pagefile. The "paging IO" counters in PerfMon include paging to all mapped files, not just the pagefile - which is why they don't drop to zero when you get rid of your pagefile.