As a member of the local Angel group selection committee, I have seen a lot of technical entrepreneur presentations to investors that are too long, but I've never seen one that was too short—maybe short on content, but not short on pages! A perfect round number is 10 slides, with the right content, which can be covered in 10 minutes. Even if you have an hour booked, the advice is the same.

Remember that the goal is an overview presentation that will pique the investor's interest enough to ask for the business plan and a follow-on meeting, but not close the deal on the spot. If you can't get the message across in ten minutes, more time and more charts won't help.

Every startup needs both a business plan and an investor presentation completed before you formally approach any investors. The approach I recommend is to build the investor presentation first, by iterating on the bullets with your team, and then fleshing out the points into a full-blown text...