Hi
I use car magnets from vistaprint, which you can get 2 reasonable large size for less than £20. There are a number of advantages to car magnets:
1) They are cheap
2) Because they are cheap, you can easily get new ones for a special promotion.
3) You can take them off very easily, obviously this is advantageous when selling the car.
4) They do work. In effect for most people if they get one customer from it, then it pays for itself.
5) As an alternative idea, you could in theory give out "free" magnets to your existing or new customers as part of a new "profit sharing" promotion. Long story short, each customer who agrees to display a small magnet on their car will get a share of "a dividend" each time a new customer responds to one of the magnets. If the customer states that they saw the magnet on, say a blue fiesta in Townsville, then if the owner can be identified, they will get X amount, and all others (to keep them advertising) will get Y.
So here is an example. Let us say you have 20 cars with your magnet (about £10 each for a dinner plate size, anything bigger would put them off, and of course this £10 is paid for from the money they paid you as a customer anyway). Because of a response to your magnet, it gets you £500 worth of work. You decide what percentage of this goes to the "dividend", let us say 10%. So that's £50, and if the car is identified, the owner gets 20% and the rest shared with the other 19 cars. If the owner is not identified, then everyone gets an equal share. So the lowest each person would get would be £2 per customer, even if it wasn't even their car that got the work.
May not sound much, but if it attracts 50 customers from 20 cars, then each person will receive a minimum of £100. Obviously after one month, each of the dividend participants must supply evidence that the magnet is on their car. This can be done by either spot checks (not easy) or for them to provide 2 pieces of photographic evidence when requested.
All the best,
Scott Burke
MoneySavingHypnotist.com