The Basics of Beautiful Guitar/Ugly Feet Detecting (BG/UFD): A few obvious tips based on my experience of this benign and relaxing hobby:
Check first:
-ads with multiple pictures: chances are there's a toe somewhere.
-never miss: ads with black,glossy guitars,and/or mirror pickguards. Interesting reflections of people crouching in summer underwear possible.
-Guitar lying on a carpet.
-Not real BGUF but welcome anyway:
Non-feet: animals, untidy messy rooms, tattoos,of course shoes and socks, etc....
Non-guitar: Guitar gear, basses , drum-kits (?) A few other instruments ( some might object to accordions for medical reasons).
UGBF : Ugly guitar/beautiful feet. BGBF, UGUF
Most-praised: Guild content. High-end super-rare hand-made expensive collector's guitar and ugly feet.Home-grown weed in the background. Weird assistant.
-Possible points for debates: are SG's more likely to be ugly-feeted than Telecasters? Ugly-feeter sociology: Do rich people possess more toes?...Rock'n'Roll Hall of Feet Award....
BG/UFD is still an incipient science, groping in the mist of Guitardom, feel free to comment and develop this memo, so that, in the end, the Tortoise-Pick of Truth&Wisdom will be shaken out of the Semi-Hollow Body of Ignorance! (That is, supposing you've got no minor scales to practise...)