When I was running advertising for a small business we put vouchers in to track advertising. The only people who brought in vouchers were people who were already customers who said they were already coming. So, we spent money to reduce our revenue. (I do the same, hunt for vouchers after making a buying/visiting decision.)

I was on national TV and national radio (UK) - none of that blipped our visitors/revenue.

Only thing that ever definitely worked was handing out flyers and chatting to people in the street (and being top of Google SERPs).