In business, everything revolves around people.
For any startup, the most important people in question are prospective customers, and for the startup cutting its teeth online, it is registered users. That being said, the single best way to measure a web startup's success in its infancy and toddler phase is number of registered users and, by extension, how well you know the people behind the numbers.
Having built an online marketplace from the ground up, we were proactive in seeking our first customers and enjoyed learning firsthand about features and benefits they hoped to see in our service. Inviting registered users to help us shape the service they were paying for produced an open, vibrant and ever-evolving web service. These early adopters became some of our best sounding boards, advocates and catalysts for growth in a highly specialized field.
When we first started, we had a whiteboard completely filled with names of people who had decided to do business with us. Each day presented an opportunity to add another name to the board so that we could see our customers as people and not just numbers. I still remember the three Bobs, two Karens, and at least one Liz. My wife at one point could name 100 customers off the top of her head because we were so invested in the people who had put their faith in our abilities.
Relationship building aside, how did we fare registered users wise? Our cumulative membership base was 2,000 in the first year, 7,000 by the end of our second year, and 17,000 by the end of the third year.
Whatever aspect of your company you are going to measure, do so consistently—ideally on a monthly basis. In your spreadsheet, you can even jot down a few notes about what happened in that month or what you did differently, allowing you to learn from your mistakes and capitalize on your greatest successes.