How to keep up with your photo stacks
Once you have downloaded the folder (DCIM or whatever) or files from your memory card, rename the pics!
Renaming photos can be done as a batch operation with programs like iView or free ones like ExifRenamer:
- They should go as something like date taken – because these names never reoccur: »yyyymmdd«
- an underscore for seperation »_«
- optional: add an event »Easter«, location »Denmark« or name »Sarah«, and another underscore for seperation »_«, when you have a whole stack from the same shoot.
- your image number, to be inserted automatically »123« (make sure to use zeros up front: start with 001, not 1).
Your file name will then be different from all the other image names you have ever had and look like this: »20090522_Sarah_002.jpg«

More tips:
When you do alterations to the image, say photoshop or resize it, and you want to keep the original and mark that this image has been changed, then you should use suffixes. For example, your photo can be called »20090522_Sarah_002a_1000px.jpg« – and you will never take the file assuming it is in original size.
I also recommend making folders in the same structure: »yyyymmdd_Name«, for example: »20090522_Sarah«
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Why all this? Now you have a definite name for every single file and will be able to search for any photo taken on any date that you can look up via your calendar and what you did that day; or any photos of Sarah, for example. When someone asks you for a certain image, you can easily look it up on your computer by using search.
The earlier you start implementing this into your work flow, the better for you (as with all improvements). You can even go back and auto-rename all of the old images you have on your computer, because the programs can read out the date from your metadata (exif).
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PS.: Always remember that any digital file should have at least one backup.

