What ever your workflow, back-up your original images first!
If your camera doesn't have a "raw" setting, you'll need to save as TIFF (more "universal" than psd). Once saved, append your file name such as this "file-name-wip" where "file-name" is the unique name you give the file instead of the generic file name set by your camera and "-wip" means Work In Progress. For info on this aspect, you can go to dpbestflow.org on file naming and metadata.
Once your files are renamed and backed up, be sure use adjustment layers to change your color, density, etc. on the file. Working on the file with tools such as burn/dodge, curves, levels, saturation, etc. directly on the image is permanent! When you are finished, save your "-wip" file and save it again as "file-name-master". Your master image can be the flattened version of your "-wip" file and can be resized and sharpened for output. When you do this step, make sure you rename the file once again with the print size, for instance.
Though you may have three or four files of your original, each will be a different version and each will have a different notation as to it's content: camera original (.jpg in your case), -wip: work in progress, -"-master", "-8x10": 8x10 flattened and sharpened file, etc.
Always work deliberately and with consistency. By working with layers, you never loose information unless the file is flattened (your ready-to-print files).
HTH,