ALWAYS eject any virtual media (CD/DVD/Floppy) once you’ve finished as failure to do so will often stop a vMotion in its tracks.
Get your NTP and DNS setup correctly, this will save you from contemplating suicide 🙂
You can never have enough memory, or storage.
Make sure you have remote, OS-less, access to your machines such as HP’s iLO system.
Keep a repository of OS/App .ISO files.
Not a direct answer to your question but in the hope that someone saves themselves from tearing their hair out in the future by finding this response – HP blade servers don’t ship with their ‘VT’-bit enabled by default, you have to enable it in the BIOS (F9). Without this ESX 3.5U4 doesn’t throw a useful error, no it just hangs prior to the code install 🙁