Originally posted on resexcellence.com. The original article can be found here: https://web.archive.org/web/19990220021352/http://www.resexcellence.com:80/resedit.shtml

ResEdit Precautions

Always work on a copy
If you do nothing else, at least do this. Working on a copy ensures that no matter how bad you screw up, you have something to fall back on. Of course if you are hacking software you can reinstall it if things go wrong, but who wants to do that?

Never throw away the original
It never fails. You perform a hack. It works beautifully. You figure "why waste the disk space" and throw away the original. Then WHAMMO! Everything goes to crap on you as if it was just lying in wait for you to be so stupid.
I simply keep an "Original" and a "Hacked" folder within my ResEdit folder. As I work on an item it gets to be stored in "Hacked" and when I'm ready to use it I put the original file in the "Original" folder for safe keeping. With a few exceptions most of what you hack will be fairly small files that won't take up much disk space.

All you can damage are files
Remeber that no matter how badly you may screw up using ResEdit you can't damage your hardware with it. It won't "break" your hard drive or screw up your processor, it can only change software and software files. So as long as you take care to back things up there is nothing to worry about.

Never work on something as it's running
As I said, work on a copy. If you try to make changes to any software while it's running the results will probably be disasterous. Especially if you're working on the System software.

Keep a Startup Disk handy
We all make mistakes. But as long as you have a startup disk (at least while your hacking the system), such as DiskTools, you'll be just fine. You can restart from the Startup Disk, swap the hacked file out for the original copy and restart.

Make a log of your changes
If you decide to become a Mission regular and you perform a lot of these hacks, you should keep a record of your efforts. At some point one of them is bound to make your machine act a little strange. Simply trace the occurences back to when they began and see if a hack is to blame.

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never open compressed image resource, allocated more memory 15 MB minimun, the best is 25MB