1. Save all your important files from the partition WinME is on and format it. You can sidestep a lot of potential problems with a clean install instead of an "upgrade".
2. Have a PCI IDE or SCSI card? Download the latest 2000 drivers and put them on a floppy. You'll need them during the install.
3. Pretty apparent, but download all the latest 2000 drivers before the installation.
4. Check to see if you motherboard is FULLY ACPI compliant. If not, when the installation is asking if you need any third-party disk drivers, hit F5 and choose Standard PC. Personally, even though my board is ACPI compliant, I find that I gain quite a few FPS in games when I choose Standard PC.
Hope that helps. There's not really anything else you can do except hope it goes through okay. I've never had any problems with installations.