Things to be aware of before your meeting with the investor: 

• Present selected aspects of your game, not everything. It can be a good idea to keep certain aspects secret.
• If you want to be absolutely certain that the investor has really understood that the information is confidential, you should draw up a non-disclosure agreement (NDA).
• Has the investor refused to sign the non-disclosure agreement? If so, consider whether you would still trust them and what risks would be entailed.
• It is often in the design of a game idea that the intellectual property value lies. Talking about it is usually relatively harmless. (NB: This does not apply if your idea is a technical solution which could lead to a patent - if it is, then it will be important that you keep it secret.) 

Investors often focus on evaluating the team in the enterprise, the competence of the staff, visions and the way in which they are looking to build their business in the future - the intangible assets.