Hi,

Get involved with your audience. If it is an app about the restaurant business, start talking to local dining establishments and see how you can work together to promote.
Another great tool (depending on where you are located) is using meetup.com to meet with like minded individuals to network on topics of discussion.
Wherever your mobile app is supposed to live (in the hands of smart phone users), go there and engage with those potential users. They will probably be excited to share with you their thoughts on the App.