What has worked for me in the past is to buy a bunch of $5 Starbucks gift cards and sit there and offer people a free coffee in return for feedback on my app.

What has worked for me in the past is to buy a bunch of $5 Starbucks gift cards and sit there and offer people a free coffee in return for feedback on my app. Another successful experiment was renting an ice cream truck and place it in front of a college and offer free ice cream for downloads.