My free advertising is copying a friend who is also a spark, I slide my business card inside the lights on the shelves at my local big diy chain, Out of around 100 cards inserted, I have had 14 calls to fit light fittings, So it has worked out very well, that's several hundred quids worth of work for very little outlay. One woman said she rang me purely as she thought it was very enterprising!
I have also inserted cards, flyers etc in books in the library, I started by checking for the top 100 books in the library and when in there waiting for my niece to finish her book club on a Saturday, I went around and put them in the said top books.. a large number of baking books coincidentally! and have had 6 customers from this method.
My other little method that did cost me a tenner is I am on good terms with a former homeless ex squaddie who I have mutual friends with, who once sold the big issue. he works in the big issue office sorting out piles for other homeless people to flog and does admin such as pitch permits etc.. well for a tenner he will insert a copy of my flyer in all the big issues for that week in the big issue office that he can get hold off. so for a tenner plus leaflets I get it out to several hundred people. I do this once a month. I have had several calls for work from this method. Its all about being imaginative and enterprising, I got these ideas from a book on guerrilla advertising