Start with a script. Either write it yourself or hire someone skilled at writing scripts for commercials. Remember, the script is about your product, so every bit of dialogue and every visual effect needs to focus on that product. Hiring someone to write your script for you can be expensive, but the end result is worth it. A well-scripted infomercial is essential to your success. You can find a writer for your script by advertising in the newspaper or in a monthly scriptwriting magazine.
Engage the audience. Plan your infomercial to include plenty of product demonstrations. Augment the demonstrations with snappy dialogue, stories and even jokes. Plan demonstrations in which you can get your studio audience involved. You're selling your product to a TV audience, but you want to do that by selling the product to your studio audience first. If the studio audience buys what you're selling, you have a better chance of selling it to your TV audience. Your studio audience can be composed entirely of friends and family, or you can advertise for audience participants. You might even offer your product free to entice audience participation.
Shoot your commercial using whatever video and audio equipment you have available. Many infomercials have a rougher, less professional look to them, so you don't need expensive equipment to shoot. Choose a location appropriate to your product or a studio. You can check the Yellow Pages for local sound stages, or you can rent studio time at local TV stations, sometimes as a package deal if you plan to buy airtime for your infomercial. Have someone standing by with cue cards on large poster board to prompt you on the script. You should do your best to memorize it, but cue cards are helpful.
Be enthusiastic. Develop a personality that shows confidence in your product. You're selling a product, but you're also performing for the studio and TV audience. You want to smile and look like you're having a great time. Make your audience believe they absolutely need your product. Over-the-top performance and enthusiasm are okay for infomercials.
Tell your audience where your product is available, but offer special deals if they order it over the phone during the course of the infomercial. Sometimes a customer may intend to purchase your product while viewing your infomercial and then forget to do it later. Hooking customers during your infomercial and getting them to follow through with the purchase on the spot means you lose less business.