Hi - two tips -
Put your phone number only in the CL ad and "hide" email. These scammers only operate through email as far as I know. A real person who is interested in your item won't mind calling you.
Second, if you do get a suspicious email, copy a sentence from it and Google that sentence. If it is part of a scam you will come up with a whole bunch of hits with the same sentence.
One thing these scammers are not, is original.