It very much depends on who you ask.
I always suggest you let Windows get on with it and choose its own settings. Where problems arise, you can tinker with things, but unless they do I seen no point in playing around with your VM settings.
If you must manually set the paging file, there is no fixed formula to do so. Some people suggest 2.5 or 3 times your amount of RAM installed as a maximum.
My own suggestion, if you must alter things, is to run your system with Windows Task Manager minimised to your system tray and do what you would normally do with your computer for a while. Check out your page file use and make alterations based on that. For Windows 9x you can use the monitoring tools in Start, Programs, Accessories, System Tools to check out your actual usage.
It's a pointless exercise devoting a huge virtual memory to a system that doesn't need it, so identify your requirements and make alterations accordingly, and only if required.
For the record, the only systems I set up manually for virtual memory are the two graphics workstations I have at work. I leave Windows to successfully manage every other desktop and notebook PC I have.