Buy your supported ESX Server hardware from a major vendor such as Dell, HP, or IBM. Ensure you spec out your hardware according to recommendations from both the ESX Installation Guide and the Systems Compatibility Guide.
Practice installing, configuring, breaking, and rebuilding your ESX software. You want a solid ESX Server when it's deployed into production. The way to get this type of solid build is to practice, practice, practice. Once you've got it down, document it.
Use clones of your template virtual machines as often as you can. Your templates should have all the unnecessary services turned off which provides greater scalability for your ESX Server.
Learning to think virtually takes time, practice, and education.
Know and follow support issues surrounding Microsoft and follow the issue as it evolves, as we're sure it will.
10.6.1.3. Common Problems
Follow the procedures from the manufacturer of the tool you use to create bootable ISOs. Don't forget, ESX Server is Linux, by placing a CD-ROM into the drive and then from the Service Console typing cat /dev/cdrom > cdname.iso.
To remedy a sluggish Windows VM, always ensure you set the Hardware Acceleration slider to Full.
Don't forget to restart your virtual machines after each reboot of your ESX Server. You can specify this to happen automatically and in any order you prefer.