How to protect code and business strategy before pitching

Software/hardware functionality may be protectable under patent and the source code itself protectable (in thin fashion) under copyright. “Pitches” may or may NOT involve the disclosure of truly-proprietary functionality (e.g., the “how” of what you’re accomplishing) and your engagement with prospective investors may be staggered wherein one will reasonably be required to execute a NDA, mutualized or otherwise, to get information about your systems beyond bullet points. Obviously, you will want to be wary of and/or avoid an “investor” who demands full disclosure and refuses to incur any associated obligations.
It may be advisable to file a provisional patent application for your technology and file an application for copyright registration for your code and pitch deck(s); the filing fees for both efforts are generally low. The copyright registration application process is very straightforward, though you should seek assistance with preparing and filing a provisional application.
Beyond these federal filings, you will want to be engaging investors – and other third-parties – in protectable fashion, and that usually involves non-disclosure agreements of varying breadth. There are many examples of NDAs online, but again it is worth consulting IP counsel to create one specific to your disclosures and goals.