I always tend to run emulators on my machine. With that in mind, I do have hours of VMs in Virtual PC, VirtualBox, VMware, QEMU, and SheepShaver under my belt. But I've first used PPC Macs in high school, and now that I can emulate them, I would like to share some of my experiences here, as well as some pointers.

Please take note that you are encouraged to give me a few pointers of your own: leave them in the comments!

My Mac OS Virtual Machine Setup

• 1 GB RAM (maximum set by SheepShaver)
• 2 GB disk (maximum usable by SheepShaver, not sure otherwise)
• Mac OS 9.0.4 (maximum usable by SheepShaver, I wouldn't DARE touch anything higher, fear of emulator crash)
• New World ROM (included with SheepShaver starter pack on the Emaculation forums)
• Ancillary software: MS Office 98, Classilla 9.3.3, Windows Media Player 7

Pointers about what I've done

• I would personally put my Mac VM to full screen at native resolution, as that provides the most screen space for my computer.
• Most of the software I use is easily available for download, and then, it's an ISO image, so it has to be mounted in SheepShaver's GUI.
• MS Office 98 does tend to crash the emulator when first launched. I don't know where I got this pointer from, but installing the Japanese language pack and disabling "Shared Library Manager" (the 68K one) in your Extensions Manager will fix that. Leave the "Shared Library Manager PPC" enabled.
• I'm running Windows 10 64-bit. SheepShaver is very picky about its settings here. Disabling automatic media polling in the config program can help a great deal IMO. 

Some Issues I Have with my VM Setup

• Although Office 98 does work, opening a PowerPoint presentation in it crashes the emulator. Not sure what causes this!
• Classilla does also tend to crash the emulator sometimes. Unavoidable.

If you have anything to add, leave it in the comments.