Items to bring. Signs, bottled water,sun glasses,
cheap camera, group business card.
Getting cars to honk isn't difficult, especially if
you look enthusiastic. I always set a goal of getting
delivery trucks, city buses and Semi trucks to honk
( big air horns in response to your signs are a rush
).
Sometimes a whole group of cars goes by without a honk
and sometimes one honks and several chime in, sounding
as if all ten or so in the passing group are honking.

We get one or two one-finger salutes but, honestly
that just tells me we are doing a good job which makes
me smile bigger and I let them see me waving and
smiling in their rear-view mirror.
Here and most places I think, the area from the curb
and back a few feet is public property so nobody can
tell you to leave but you might need to think a bit
more about where to park if there happen to be several
unfriendly businesses in the area. We've never had any
real problems in this area.
Obviously you want to post the event as many places
as possible. Our local Democratic County Party puts it
in their newsletter, it goes in the T-Town DFA event
posting, the Impeach Cheney First (meetup)posting and
the Tulsa Impeachment Committee ( ImpeachOk1.org )
posting as a minimum.
Take a sign, a wave and a smile and you'll have
fun.