• Add a splash screen, the very first thing your users see after they select your app.
• Use AppLoading to ensure your interface is ready before the user sees it.
• Preload and cache your assets so your app loads quickly, even with a poor internet connection.

• Configure the status bar so it doesn’t clash with your interface.
• Use native gestures whenever possible.
• Use interface elements that make sense on the device. For example, see the iOS Human Interface Guidelines.

• Add a great icon. Icon requirements between iOS and Android differ and are fairly strict, so be sure and familiarize yourself with that guide.
• Customize your primaryColor.
• Make sure your app has a valid iOS Bundle Identifier and Android Package. Take care in choosing these, as you will not be able to change them later.

• version will apply both to iOS and Android. For iOS, this corresponds to CFBundleShortVersionString, and for Android this corresponds to versionName. This is your user-facing version string for both platforms.
• android.versionCode functions as your internal Android version number. This will be used to distinguish different binaries of your app.
• ios.buildNumber functions as your internal iOS version number, and corresponds to CFBundleVersion. This will be used to distinguish different binaries of your app.

• Use Constants.nativeAppVersion to access the version value listed above.
• Use Constants.nativeBuildVersion to access either android.versionCode or ios.buildNumber values (depending on the current platform)

• Starting October 3, 2018, all new iOS apps and app updates will be required to have a privacy policy in order to pass the App Store Review Guidelines.
• Additionally, a number of developers have reported warnings from Google if their app does not have a privacy policy, since by default all Expo apps contain code for requesting the Android Advertising ID. Though this code may not be executed depending on which Expo APIs you use, we still recommend that all apps on the Google Play Store include a privacy policy as well.

• All apps in the iTunes Store must abide by the App Store Review Guidelines.
• Apple will ask you whether your app uses the IDFA, the answer is “yes.” This is because Expo contains the Facebook and Branch SDKs, which contain code for collecting the IDFA, and you’ll need to check a couple boxes on the Apple submission form. See Branch’s Guide for which specific boxes to fill in.

Note: No data is sent to Branch, Facebook, Segment, or Amplitude from your app unless you explicitly do so using the APIs. For more information on how Expo handles your data, and your end users’ data, take a look at our Privacy Explained page.

• Permissions are configured via the android.permissions key in your app.json file
• By default, your app will include all permissions supported by Expo. This is so that your standalone app will match its behavior in the Expo client and simply “work out of the box” no matter what permissions you ask for, with hardly any configuration needed on your part.
• There are some drawbacks to this. For example, let’s say your To-do list app requests CAMERA permission upon installation. Your users may be wary of installing since nothing in the app seems to use the camera, so why would it need that permission?
• To remedy this, simply add the android.permissions key in your app.json file, and specify which permissions your app will use. A list of all Android permissions and configuration options can be found here.
• To use only the minimum necessary permissions that Expo requires to run, set "permissions" : []. To use those in addition to CAMERA permission, for example, you’d set "permissions" : ["CAMERA"].

• It’s helpful to glance over Common App Rejections.
• Binaries can get rejected for having poorly formatted icons, so double check the App Icon guide.
• Apple can reject your app if elements don’t render properly on an iPad, even if your app doesn’t target the iPad form factor. Be sure and test your app on an iPad (or iPad simulator).
• Occasionally people get a message from Apple which mentions an IPv6 network. Typically this is just Apple’s way of informing you what kind of network they tested on, and the actual “IPv6” detail is a red herring. All of Expo’s iOS code uses NSURLSession, which is IPv6-compatible. More info.

"infoPlist": {
  "NSCameraUsageDescription": "This app uses the camera to scan barcodes on event tickets."
},

  "expo" : {
    ...
    "ios" : {
      "infoPlist": {
        "CFBundleAllowMixedLocalizations": true
      }
    },
    "locales": {
      "ru": "./languages/russian.json"
    }
  }

// russian.json
{
  "CFBundleDisplayName": "Привет",
  "NSContactsUsageDescription": "Эти слова по русски"
}

Source: Deploying to App Stores – Expo Documentation