In the beginning to have to grind it out. Figure out who your audience is and go spend time with them. Leverage your network. Ask friends, family, previous co-workers, and professional networks. Give them enough details to know who it is that you are looking to talk to.

For example, if your app is for young professionals that are seeking employment after graduating for college, tell your network! Be specific. Ask for what you want.

"Hello {your friends name here}. I am looking to get in touch with {your detailed description of your ideal customer} who would benefit from {your value proposition}. Can you introduce me to anyone that may fit that description?"

The other thing you can do is provide an invitation opportunity. It is always easier for people to give out an invitation than to tell their friends to expect a sales call.

If you want to talk more about it, give me a call and we can talk about user acquisition methods.