1. build something worth investing in
2. make sure people know about it (tell your friends, don't work in a silo, etc.)
3. have the right friends (i.e. be plugged into the community, be friends with other founders, be in a place like San Francisco, etc.) and loop them in to what you're doing
4. if all of the above happens, I will likely hear about you from someone I trust
Almost all of my investments come from a trusted referral.
Also helps: join YC or something similar (few are as good, though)