Nice guideline, amusing tips included.
CL is a perilous place full or scammers, spammers, and misleading ads. But there are also good honest people, you just have to use good judgement and weed out the crumbs.
Beware and use your gut check on questionable ads.
Question the seller via email reply, hesistance or irritation to specifics indicate seller ignorance or potential dishonesty.
Deciphering what the ad says and sometimes more importantly, what it doesn't say. Skewed photos, night photos, a single or very few photos, only one side photos. Another key is observe photo backgrounds and scrutinize it carefully, it can be very telling.
I've bought and sold dozens or cars, trucks motorcycles, and other things on CL without incident but I am very cautious and thorough.