In a perfect world, the best way to keep a prospective client from taking ideas you share during a pitch is to have the prospect sign a confidentiality agreement before you make your pitch. I suggest my clients use a short, easy-to-understand evaluation confidentiality agreement indicating that my client is disclosing confidential information to the prospect for the sole purpose of evaluating whether to enter into a business relationship. It obligates the prospect to keep the information confidential, to not use it for any purpose other than evaluating the potential relationship, and to return all confidential information upon my client’s request or if they decide not to engage my client. It covers all confidential information you disclose for the pitch, whether verbally or in writing, even if that information was disclosed before the confidentiality agreement was signed.
A prospective client might take the confidentiality agreement idea up a notch. The prospect might also disclose its confidential information to you to help you prepare your pitch. In that event, the prospect may ask you to sign a confidentiality agreement. That’s fine. Just make sure it’s mutual; that it runs both ways, protecting the prospect’s confidential information and your confidential information. Your prospect may even have a form agreement it wants you to sign. Again, that’s fine, as long as you confirm that it provides the protection you require. I recommend getting a lawyer’s input on any contract presented to you before you sign it.
Some businesses won’t sign a confidentiality agreement for a proposal or pitch. In my experience, this is a common practice among large companies. In those instances, they will ask you to trust them. It’s a risk. Reduce that risk by prominently marking your materials (including presentation slides) as “confidential.” Also, include a proper copyright notice on your materials. In addition, carefully consider what confidential information you will include in your proposal or pitch. Perhaps you can tease some information, rather than disclosing all of it. Lastly, if you are not chosen for the project, ask the prospect in an email or letter to return the information, or to certify they have destroyed the proposal or pitch materials. Then, keep your eyes and ears open to observe whether the prospect or the contractor who won the job appears to be using your ideas.