Some gyan on media planning

Advertising can never be an expense, it must always be an investment. There must be at least a 75% expectation that the advertising will reach and produce more in sales than it will cost to place. If you don't have that 75% expectation then you should not place the advertising.

Who and where is your target market? - If you are selling farm equipment, are your customers in town or on the farm? Right. On the farm. So why waste advertising dollars that reach town people who are not your target market even though that media may also reach your target market? See the next point for more on this.

Cost per thousand? - Remember point one from above? Advertising must always be an investment never an expense. Media sales people are going to talk to you in terms of cost per thousand. This is the per person cost it takes to reach their audience. Notice I said "their audience" not your target market. So how does my farm analogy from above fit in here? What you should be concerned with is cost per customer. How much does advertising cost to bring a target market customer into your place of business? Cost per thousand is immaterial if most of the audience is not your target market. The cost per customer would probably make this advertising too costly for a satisfactory return on your advertising investment.

Which forms of media are best in small towns?
These will of course vary depending on the size of the town and media that are available to you. It will also vary depending on the size of your target market within your sales area. In many cases the size of your town will have a lot to do with the forms of media you choose.
For example, if we use the farm equipment analogy from above, you don't want to advertise to the people of the town who are not your customers. You want to reach rural customers who farm for a living. So in this case I would recommend direct mail. I can target rural routes with fliers or postcard mailers just for that market for much less than a newspaper ad or radio spots. See: Direct Mail: Why It Works And How To Use It.
Suppose you were a real estate agent and every morning when you walked in your office, there on your desk, would be a list of people ready to buy a house that day. They qualified for the credit, and were ready to buy. All you need to do is show them your listings.
Would that make your life easier? What would a list like that be worth to you? Well, that's sort of how direct mail works.
Who is most likely to buy?
As far as I know, no such list exists. But what you do have is a direct mail list that will tell you, based on past history, surveys, industry studies and collected information, a profile of the person most likely to purchase a home.
The most likely home buyer might be X years old, is married, has X children, makes X dollars per year, has X years of education, favorite pastime is X, hobby is X, favorite car is X and so on.