[wrath]

I think @nunobrito covered most of what I wanted to say.

Without knowing your product it's hard to give you the best advice, but here are things that worked for me in the past:

* Use real data that they can relate to. For example, if you're software does case management for non-profits. Find out who their customers are and create an "fake" example of how your software would work to manage a case for that company, from start to finish. This is partly for the 3 minute presentation, but more so for the barrage of questions you'll get asked afterwards once they like what they see. It's always easier to sell something when you find a solution to a pain your customer has right now, with one of his customers!

* Use only the terminology that they use and understand. Similar to #2, use the language that your customer speaks. Know your user and which language and acronyms they are using on a daily basis. I've seen so many times young startups use scientific terms or executive mumbo jumbo that the audience didn't understand.

* The 3 minutes is only the beginning. Whether you succeed or fail, it's not the end. Before, during, and after, identify the lead of the group that will be using your software and try to identify the decision maker. The person who signs the check if often different then the person evaluating your software. This is a sales cycle and they are both important for you to convince. Get a meeting with them, figure out what makes them tick, what their budget is, when will they be in a position to evaluate your software, etc..

Hope this helps a little, good luck!