I thought for a moment and realized I had no idea.  So I started some research.  Here’s a couple of items I found:

• Check that your BIOS is current.  There are constant bug fixes and additions to BIOS and I’m a big fan of preventative maintenance. Once you update it, check your settings again as some updates change default settings.
• Turn on VT Extensions.  This will allow you to run 64-bit guests in ESX.
• Turn off any CPU power saving features like "Cool’N'Quiet" or "PowerNow" or you could end up with time sync issues like this article describes
  
• Another possible issue I found was if the Excute Disable Bit in the CPU settings was disabled.  This can cause vMotion to fail as described in this article here .  So you would want to enable the Execute Disable Bit.
• Processor Adjacent Sector Prefetch set to enabled as per the IBM Redbooks and Processor Hardware Prefetcher set disabled.  I was not able to find a IBM link to verify these two, I found them in a VMware communities thread here .  There’s a really good description in this thread as well.  I would disable both.
• For the memory setting, the most common recommendation I’ve read is to leave it set to HPMA.  You can read additional details and find more info about this setting in this communities thread .
• For a good explanation of BIOS settings in general and what they mean, have a look at this article: "BIOS Settings Demystified"

I’m sure that there are more settings that I could not locate.  Please feel free to comment on this article with any additional BIOS setting s0 that you are aware of on IBM hardware and please document as much as possible.

I will be posting a summary of BIOS  recommendations for HP and Dell within the next week.