Could please explain this to me in a more step by step process?
Sure. First thing is to have a plan. The plan may change later, but the better it is to begin... Either name every image such as (Bird_Sparrow_01.jpg) or create folders with names like (Bird_Sparrow_20080712) and put all the sparrows from the 7/12/2008 shoot into that directory. You could begin the folder names with the dates, but then to find the sparrows would require additional work. Another option is to create a document (or spreadsheet, or database) and keep a log of each image there with the filename and foldername and comments.
The disadvantage of not naming the individual images is that they're harder to find when you don't, in fact nearly impossible to get to. You can read all of the questions and comments here on LL to see how many people just can't get to their images of a particular subject because their file management is done by an image editing program (very bad), or worse, no management at all.
Once you have a plan that allows you to search for the files you want to see, get a copy of the DIRMATCH program, or whatever the latest equivalent is from the Internet. My copies are highly customized and would not be suitable to hand over without tutoring. With Dirmatch, you can easily compare folders on your working computer with folders on your backup external hard disk.
If you have a *lot* of folders, then you need to consider two things:
1) Try to have "archived" folders that you do *not* need to compare, back up to, or otherwise examine frequently. Then the remaining folders are your "current" folders that you will Dirmatch frequently. This saves time folder-matching.
2) If there are a lot of current folders you make changes to (changing, adding, or deleting images), then (on Windows systems) you can create a "Batch" file that will execute the Dirmatch program for a whole range of folders, one by one, so you don't have to manually specify the source and backup folders for each folder in your current list.
I don't know if Mac computers have such a thing as a Batch file, or any user automation at all, sad to say.
A Batch file may look like this:
Dirmatch C:\Folder_A E:\Folder_A
Dirmatch C:\Folder_B E:\Folder_B
Dirmatch C:\Folder_C E:\Folder_C
Dirmatch C:\Folder_D E:\Folder_D
............ and so on
With this batch file, all I have to do is click Exit when I'm done with each compare, and the computer executes the next line automatically.
I maintain about 30,000 current files in about 300 current folders, with approx. 100 different files changed each day. Since I don't know at the end of the day which folders have the changes (they're somewhat random), the 300 Dirmatches I execute take care of all that, and the backup takes only a few minutes. In fact, I have about 6 or 7 backup drives, all identical, and all get updated within the course of a week. And each backup session is just a few minutes.
**Important note: I cannot use a totally automated backup program, because those programs always copy the newer file to the older file, or the computer disk file to the backup disk file. This is not acceptable to me for reasons you will discover when you get to that point. Dirmatch allows you to easily copy the new to the old (or to a folder on the backup drive where the new file doesn't exist yet), and copy many files with one click. But you can also decide when not to do that and go the other way when necessary. Sometimes I may copy just one or two old files to the newer copies on the computer drive, and then copy all the rest with one click the normal (new to old) direction.
Intelligent backups and file management observe one extremely important principle that should never be abrogated: Never copy a file over top of the same file on a backup media if the file hasn't changed. You could be copying a corrupt file over top of a good one.