Start off by writing "Have a Great Day" or something similar on ten of your business cards. Always carry this special batch with you so that you are ready to use it when the opportunity presents itself.
For Instance:
Pay the toll for the car behind you, Give your card to the toll person and ask them to give it to the car behind you and let them know that the toll has been paid.

I often do this and I have gotten both great network contacts and business out of it. You might want to consider targeting this approach. If you are selling Luxury Yachts, maybe a Ferrari or Lexus would be a better choice than a 1986 rusted Chevy. However, this is such a low cost approach that you can just make it a standard whenever you go through a toll. You can also do this in other ways, Pay for lunch for another table, and ask your waiter or waitress to hand over the card for you instead of the bill.

If your cell phone number is on the card, you might want to have it handy. I get a lot of calls immediately after the car behind me pulls through the station.

This is a great way to make an initial connection with someone that can end up giving you references and business in the future.