Maintain careful, complete, and accurate records of everything you do. This includes records of your meetings and financial transactions, any media coverage, and your public relations material. This level of record-keeping is necessary to meet legal requirements and to establish a paper trail. In this context, a paper trail is a verifiable history of your organization for presentation to potential funders.
Collecting your organizational history will give you as much credibility as possible when approaching a potential funder, so keep that in mind at all times. Operate on the assumption that they do not know you and are going to be wary of anyone they do not know coming along and asking for money. You must prove your legitimacy, and having a historical record will help you.
If your organization is so new that the history is too short to present with any degree of confidence, adjust your narrative slightly to explore the history of the individuals who started the organization and tell their stories. Explain how they came together to form this new organization. Press clippings of their activities will give the reader the needed tangible record of who you are even if the articles don't discuss the organization itself.Keep a Scrapbook
Sometimes the simplest practices are the most effective. Maintaining a simple scrapbook of your organization through photographs and media clippings will do more to show who you are than more high-tech methods. The book can be a simple loose-leaf binder filled with material about your founders, your board, and your current activities. It will bring everything into perspective.