1. Networking is actually a very bad way to secure initial customers. It is very unlikely that you are going to find yourself in a room with your target customers. You'll end up wasting time and energy on people who are never going to use your product.
2. Develop a persona for your target customer. Make it tangible so you can imagine your end-user. Imagine how they go about their days. What their interest are; what their hobbies are. What they do in the morning; what they do at night. Their fears and challenges. What is the challenge that your product is solving for these people?
3. Now, you should have a sense of who you want to reach. It might be quite a broad category... 'Heads of Business Development in start-ups', 'Design freelancers on PeoplePerHour'. At this point you should be in a position to think about where you might be able to find lists of these people. Go niche, so you don't overreach. It's easy to capture a small market than a big one. Start small, and grow to new markets. Maybe, if you're building a freelancer website, it'll mean dialing down your target market to 'design freelancers in Aspen'. Try to find a directory of people online that meet this category.
4. Create a database of all these people. Only start with 100. It should have their names, companies, email addresses, and a notes column. Fill all this data in. This is a list of potential early adopters.
5. Draft these people a short, targeted email laying out in CLEAR and DIRECT language your valuable proposition. 'I spotted your were a design freelancer in Aspen. I'm building... I thought you might be interested because... Is this something you might want to use?' Follow up a week later with an even shorter note for people that didn't reply. RESPECT their details. Don't spam them. This is a PERSONALISED message.
6. You will receive two responses (a) 'yes' -- that's great, you have an early adopter; track their use of the service and value them; (b) 'no' -- that's even better, ask them why they don't think it's a good fit for them; ask them for feedback; why isn't it attractive; what would make it attractive?
7. Fill in your database with all these responses. After you have 20-50 responses, you have some important intelligence about whether you have built a product which ACTUALLY solves a market problem (i.e., you have market fit); if not, pivot -- build a product that responds to these people's feedback.
8. Rinse and repeat.
Sorry for the plug... people have told me that the most time consuming bit of this process is finding these people and their emails. That's why I built Find Emails Team. You can find it here: http://findemailsteam.com. For a few dollars, we can put a manual team to work to find these contact details for you.
Best of luck!