Here's an excellent guest post on TechCrunch EU by Alan Gleeson, making some useful points both about how to get traction, and how to present it to potential investors. the article is long but full of useful information and worth your time. A choice extract:
The most persuasive evidence you can provide that your business is worth investing in is â€˜evidence of demand'. Clearly if this demand is translated into sales you have irrefutable evidence that the start-up has traction. The greater the sales the greater the proof.
In terms of the â€˜traction hierarchy', active users and letters of intent probably fall into the next tier below real sales, finally followed by viewer numbers (on your website). While growing visitor numbers to a website was once a good barometer of the potential of a business, it is no longer considered a valuable proxy. These visitors have to convert to sales and hence once again the focus returns to the one piece of evidence that trumps all others - real sales.
It also links to this excellent post by Gabriel Weinberg of Duck Duck Go, which lists a great many ways to acquire initial users.