I previously wrote about the fear of someone stealing your ideas. What’s important is that you believe in your ideas enough to put massive effort into developing them to the point that you dominate the sector with your implementation.
Once you have done this, you should have no fear in sharing them. Gone are the days that a VC is going to sign an NDA. So share your ideas with them, secure in the knowledge that you have developed them so far that no one else can surpass you. Tell everyone that you know what you are up to in order to get word of mouth excitement brewing. Free of the worry that you are giving away the “secret sauce” to your invention and your future.