
Regarding the RAM requirement, VMware and virtual machines in general perform best with a lot of RAM, if you plan on using them often on your Mac it’s highly recommended to upgrade to 8GB.

If you’re serious about Lion development, remember that virtual machines have their limitations, and you should probably just setup a dedicated partition to run the developer preview directly. This is really only recommended for more technically inclined Mac OS X users. If you want to run Mac OS X 10.7 Lion Developer Preview but you don’t want to bother setting up another partition or upgrading your existing Mac OS X 10.6 installation, you can go with a third option: running Lion in a virtual machine with VMWare.

The older method is repeated below for posterity sake: Installation of Lion is extremely fast, and you are then able to boot and use your virtual OS X 10.7 install. Choose Continue and select your settings, and boot the VM.Locate the “Install Mac OS X Lion.app” (here’s how to redownload Lion from the App Store) in your /Applications/ folder and drag that into the “New Virtual Machine Assistant” window.
