Treat the VM exactly as you would in a physical environment with similar resources.
Please review the following Microsoft KB article, entitled "How to determine the appropriate page file size for 64-bit versions of Windows Server 2003 or Windows XP"
as the other poster says treat the guest exactly as you would a phyiscal box the windows OS has no idea it is not running on phyiscal hardware. I create a Swapfile Volume on my storage and create a LUN to hold a swap drive, I do this so as to exclude the Swap file from any Snap shot I am doing
Tom Howarth
VMware Communities User Moderator