Persistence is the key! Continuous marketing efforts will make your app successful in the long-run. Here are some suggestions to attract new users and keep your app top of mind for current users:
Include app links and mentions in your various social media networks such as Facebook, Twitter, and Instagram. Promote your app daily after you launch it then taper off to weekly or bi-weekly mentions. However, ramp up promotions for your app ahead of big events and conferences and encourage downloads by promoting specials and giveaways exclusively for app users.
Include links to download your app on the front page and along the side or footer navigation areas. Create a dedicated web page specifically for marketing the app. Add a Metadata Tag for iPhone users who visit your website via mobile so they will be notified your app exists along with a link to download it.