As mentioned, plenty of pics. If an ad doesn't have a pic, I won't even open it.
I never post my phone number, always correspond through e-mail.
I give a full description of the good AND the bad.
I personally don't like the "haggle/used car game".
I set my price fair and exactly what I want to get out of it and say "FIRM" after my price.
I also state that as soon as the item is sold, I will immediately remove the ad, so "please
don't ask if I still have it".
I list my town but not my actual address.
And regardless of your past experiences,
my "Golden Rule" is to always treat a buyer like you'd want to be treated.

If they can take the time to call you, they can just as easily respond through your ad via e-mail.
Yes, there are scammers that find "coded" phone numbers as easily as the ones typed out.
Why put your Ph. # out there period !?

Who wants to be woken up at 2:00 AM with :

"Ya man, I was wondering if you still have the pin thingy?"
"Shut up Martha, I'm on the phone"
"So dude, will ya take $200 instead of the $3200 you're asking?"

Jumpin jee-hos-if-fats !!

It's so much simpler to NOT list your phone number!