Open the yellow pages or business section of your local phone book. Look for businesses that may or may not have a radio or television jingle. You're looking for a smaller business that could benefit from a catchy tune. This could also be a new business in the area.
A jingle is a short "theme song" for a business or product. Write a jingle that is exactly thirty seconds long. This is the basic ad time for radio and television. The jingle should have a memorable melody. The lyrics should mention the name of the business, their basic services or goods, and their location.
Write a couple different versions. Record all of them or the best one. Make sure your recording is the best quality you can get at home. Sound effects are sometimes appropriate, but whatever you do, make sure the lyrics stand out clearly. You'll have the most success if you can present a radio-ready jingle to the business on a CD.
Take your finished recording and a cover letter to the business' manager or owner. Tell them you like their company and recorded a jingle to help them draw in more customers. Play the jingle for them (you may need to bring a cd player).
Determine your price. Be prepared to negotiate a fair price that is both cost effective for the business and also enough compensation to make it worth your effort. For a smaller business, $200 for a thirty second jingle is fair. For a larger company, some sell jingles up to $5,000.
They may ask you to change the lyrics, or completely rewrite the jingle from scratch. That's okay. The important thing is to establish a connection with the business. They may not need a jingle right now, but they might someday.
For your protection, it may be a good idea to draft a basic contract for you and the buyer to sign. It needs to include language that releases your full license of the jingle to the company. Once this is executed, and you have received payment, the jingle becomes their property.