When you get back from Walt Disney World, your kid’s sporting event, or wherever else you were taking pictures, copy them to the computer and then burn them to a CD, DVD, and/or copy them to an external hard drive.
This separate copy is your archival copy, the one you will revert to in the event something happens to the one you are working on or keeping in your computer.
Things DO happen, hard drives DO crash, and no matter how careful you are, overwrites DO happen so make the copy first to be safe.
You would NOT want to go on an expensive Disney vacation and have lots of wonderful photos on your memory cards only to lose them to a computer failure, a lost memory card, or other unforeseen occurrance.
So, making a copy as soon as possible is a way to ensure that will not occur. If you take a laptop on vacation with you, or if you have a copy device such as an Epson P-2000 (an item I am LOST without), copy your photos as soon as possible.
Now that you have a backup copy, you can work on your photos to your heart’s content. Do not EVER EVER EVER work on your original files. If you make a mistake and over-write them or delete them, they are gone and you are not going to get it back. Don’t you wish you had a backup??? In my haste to get something done or out of plain laziness, I have worked on the original countless times and have been burned on this. This also applies to those cameras that shoot in RAW (such as .cr2 or .nef). Even though you can’t destroy the original by editing it, you CAN delete the file or lose it to a hard drive crash. So follow this advice.
When you are done working on your files in the computer (resizing for email, fixing minor problems, or doing any major photoshopping), I recommend you save that file (ie. DSC0000.jpg) with a unique name, such as DSC0000-1.jpg. The next time you make a change to the file name it DSC0000-2.jpg and so on. This will allow you to keep track of your edits. This way you can immediately tell the original from the retouched file, and you won’t accidentally save over the original.
Memory and storage are very inexpensive these days, so take a few extra minutes to insure your precious memories. This will help insure you won’t be heartbroken later.