Analyze your competitors in search. Understand what keywords they are ranking for. Knowing the potential keyword field of your competitor is sometimes up to 80% of your success. In any case, you should know what region and search request your app should be searched for before you start to promote iOS apps.
Optimize your keyword field. ASO for your iOS app is a bit tricky. While Google Play indexes the description of the app page, you have to fit all core words and phrases into the App Store keyword field. The words may repeat in the field, but you should make your keyword cloud as wide as possible adding as many keyword cores as possible. Minimize the number of tails in the keyword field.
Index your application in search. Either a new app or ASOed one, you need to move the app by the keywords in search. When you update the iOS application, the application will get a boost and get in some 200-230th position in the search for the keywords in the keyword field. However, it will gradually go down the ranks way to out of the index. To push them up the search instead, you need to promote the iOS app by keywords. Alternatively, you can use search ads at the App Store.
Move your app to the top of App Store search
Keyword promotion is a cheap and reliable way to get a source of organic traffic for your application in any Tier 1 region you need. Make sure you go through the next stages before you start iOS promotion with installs:
When in the index, try to promote your app with 10-15 installs per day by a relevant word or phrase. Your first objective for the iOS app is to get to the 20th position. There, increase the number of daily installs by +35% per every two days. It may take from 7 to 21 days till you get to the top of App Search.