I used to do this a lot, for the same reasons that you've stated. The old snaps from an album can be inspiring. The others have mentioned above how to use the proper equipment (mostly old) and techniques to first get on your negative an ancient looking image. Uncoated or older triplets should give you that. Look for an old box camera which shoots 6x9- its lens is also bound to be uncoated. Box cameras are also prone to blurring due to the clumsy shutter release arrangements many of them have. The imprecise lens placement also contributes to that 'focus-unfocused' look which many of the old snapshots have. An old folding camera with a rickety lens board should also do this.
A photo shot on 35mm film should be admissible too. Granted that is, you shoot with an old 35mm camera with old-style film. Get an old Zorki with an old Industar and some Era film. That should get you started. Develop the Era film in softworking developer.
It was the "Chinese connection" years ago which allowed me to mimic the 'old' look. I had access to Era and Era bromide paper. The single weight fibre based paper made in China have a lot in common with the papers they used decades ago. Sadly, I couldn't get these films and papers now.
Print as you would normally. You can age the photo by using sepia toner (two bath bleach/sulphide toner) in a peculiar way. You could do one of these things:
#1. Don't wash the print well. Then bleach and tone. The remaining hypo would react with the bleach and cause the highlights to burn out a bit, simulating fading from age. The residual chemistry also reacts with both bleach and sulphide which will give variable and random streaking, as well as staining in the highlights and paper base. Using a 'tired' fixer will help- as it is loaded with silver which can deposit in the paper fibres. The sulphide toner loves these and causes the paper base to stain.
#2. Wash the print well. Then bleach with with the toner bleach. Don't bleach all the way, but stop the moment the highlights and midtones are gone, leaving only the shadows. Wash quickly, and then expose the print to bright sunlight until the bleached portions darken again. This is like doing a simulated POP print. The image will not be exactly black or brown. You may find some shades of lilac and rose there. Xiamen or Shanghai bromide paper did this quite well.
#3. Wash the print well. Do the instructions given in #2. But this time, give the print a very short dunk in the sulphide bath. It would help if you could dilute the sulphide bath 4 fold to restrain its action. Then just as the print is about 75% redeveloped, pull it out and wash thoroughly. Then put it back in the bleach bath for as long as it will take to bleach it again. After this, you have to option to put in in the sulphide bath again, or just expose it to bright sunlight. Either way, you get a print with confused shades of black and brown- just like in an aged print.
All of the techniques above deal with toning- but not following the 'correct' method. When followed as instructed, the bleach/tone process will often just lead to yellowish sepia brown tones. Quite boring . But when 'bastardised', it really gives unpredictable, yet more interesting tones.
Then when the paper just looks the way you like it, wash it and remember to harden it. I used drum glazer (that large rotating heated drum with a polished chrome surface). The finish is just like the old glossy snapshots.
To put the icing, trim the edges (remember to print with borders!) using a deckle edge trimmer. Another China connection- the trimmer which I used also came from China.
BTW, are you the same Hamster at RFforums who asked for shutter curtains? I have some now.