When should I start preparing an iOS app launch?+
Two to three weeks before the release date. That leaves time to finish the App Store page, nominate the app for featuring, which Apple recommends about three weeks ahead, and line up launch sites that have queues.
What do I need before submitting an app to the App Store?+
A name, subtitle, keywords, screenshots, a support URL, a privacy policy and the App Privacy details in App Store Connect. Apple will not let an app be submitted without its privacy details.
What should I do on launch day?+
List the app on a few launch sites and directories, post in one relevant subreddit with a single link, reply to every comment, and tell your beta testers it is live.
What should I do after launching an app?+
Keep posting in one new place a day, reply to App Store reviews, watch App Analytics for the weakest step between impression and download, and ship a first update you can announce.