1. Keyword ResearchMake a big list of keywords for your app well before the launch. Then choose the ones with high traffic. Make sure it is relevant to your app (Even though not 100%)
2. Use the keywords effectivelyApp Name, Sub Title, and Keywords field is the most important place to add keywords in iOS. Do not repeat keywords. Means, keyword in App Name should not be used in the keywords field. Remember that App Name and Sub Title fields having more weightage than the keyword field. Always use single words in the keyword field with a comma and no spaces.
3. Choose the best categoryStudy the market well and select categories in which you could get to better Top chart positions. If the category is highly competitive, it will be really tough to crack Top 10 or Top 5.
4. Create best graphicsThe icon should be unique, visually attractive, and related to your app. Screenshots can have text to explain features. Make sure to create a stunning preview video also.
5. Manage reviews and ratingssAlways try to keep the rating 4.0+ because it is the minimum limit at which users consider it as a good app. Ask for a review at the right time. Always respond to good and bad reviews. Help and fix the issues regarding bad reviews and convert them to good reviews. Keywords in reviews help the app ranking. It is OK to ask your friends to include keywords in reviews.
6. Limit the app sizeMake sure to limit the app size maximum possible. Below 50MB is ideal. It may not be possible always. But try to keep it under 100MB.
7. Have a budget for advertisingIt is really important to spend money on paid ad campaigns. This will boost your organic installs. Plan to start and stop campaigns as per your budget and organic download volume.
8. App updates are essentialTry to update the app at least once in a month. Apple loves updated apps and it gives a download boost. You may experiment with keyword / graphic updates during each update to test the effect on downloads.
9. Use a tracking tool
Make sure to track your keyword positions, installs, category positions, conversion rates, and reviews using any App Store Optimization tool regularly. Track your competitors also.
10. Promote in Social MediaCreate backlinks in maximum possible places and post regularly in all possible social media.
11. LocalizeLocalize the app and the listing if you are targeting globally. It can be in phase 2 if on a tight budget initially.
12. App UsageDo whatever you can to get the users back to your app more frequently. App usage is a really important ranking factor. It can be push messages, offering coins, special offers, login bonuses, etc.
13. Referral SystemTry to include a referral system within the app that gives benefits to the user, if possible. Always try to design it in such a way that Referrer and Referee gets a benefit.
14. Improve the positionsThe primary goal should be to improve the keyword ranking of all high traffic keywords and improve category ranking. There are many ways to achieve this other than the tips above. I will be writing another detailed article for the same. I know apps that are really ordinary/ simple which are able to generate millions of downloads by using effective ranking methods. You may contact me if you need any specific details.
15. Get ASO Help
Try to learn ASO yourself. If you are too busy and if the budget allows, hire an ASO Expert to manage this effectively.