Always take snapshots when the guest is powered-down.
Although in VMWare Workstation you can take a snapshot at any time, you cannot clone a snapshot taken of a powered-on guest.
So for example, I patched a new Windows Server 2003 guest OS with dozens of Windows Updates, installed SQL Server, installed and configured SQL Server Reporting Services, etc. It took hours. I made snapshots at each phase, and indeed was able to revert back to one after screwing up royally. However, when I later went to clone the "all patches" snapshot to re-use the guest somewhere else, I was unable to do so because the guest had been on when I took the snapshot. I pulled out all my teeth in frustration and smashed them with a hammer, then began uninstalling everything after the patches.
Check the guest firewall settings if you have host-to-guest network problems
If you have double-checked that the virtual network settings are not to blame for an inability of the host to communicate with the guest, then ensure the guest firewall settings are not blocking incoming requests.
In my case the guest was using bridged networking and could ping the host and connect to the internet via the LAN gateway. The host could not ping the guest, the reason being that the guest firewall disallowed incoming echo requests by default. Further, since I wanted to use the guest as an http server, I needed to allow http requests at the firewall level. The agony preceding this discovery was akin to a hot knife stabbing repeatedly into my liver.
32 bit guests created on a 64 bit host can only be deployed on a 32 bit host if the deployed host hardware supports 64 bit processing
This one is counterintuitive. Just because it's a 32 bit guest doesn't mean it's going to run on a 32 bit host.
Newer machines tend to support 64 bit processing. Older ones don't. It's entirely possible that a host will be running a 32 bit OS but be 64 bit capable. How do you know? Download CPU-Z and it will examine the hardware and tell you. The VMWare CPU Identification Utility might also help, but I'm unclear as to whether it just checks for a 64 bit OS, or hardware 64 bit capability.