App Icon, Screenshots and Banner
App icon, screenshots and banner are 1 of the most important things in order to make a successful app, why are you asking? Let's talk about it:
Users see your icon compare to others, this is your first 'trap' to make him click on your icon app and not on your competitors, attractive and bold icon is MUST, how to make it correct? Design is more art than math but we still have common rules to stick on:
1) Combination of 'Strong' and 'Weak' colors, compare your icon to other apps and ask your friends "what is the boldest icon from this list?" if they point to your icon that's mean you did a great job!
2) Make the idea of the app very clear, from the icon user need to understand about what this app or at least the general idea.
3) Less Text! in general, to add "Online", "3D", "New" or other super short word is ok but remember that the app icon in a smartphone is super small and too much details is a bad idea, if you decide to add text, make sure about the clear font and color and not more than 2 words!
4) Keep it simple - Don't try to add too much details, keep it clear and simple.
5) Nice design - I don't need to explain to you if something is 'looking nice' or not, even if you are not designer you understand that easily, compare your icon to your competitions and not to your previous works.
6) Are you not a brand? Don't try to look like! to add an icon with 1 character (or 2) like Netflix for example will not help you to attract users.
From those icons for example you can easily see combination of weak and strong colors, that's super bold and the idea behind each of them is very clear.
1) Make screenshots that show the most interesting parts of the app/game.
2) Put a text in the bottom/top of the screenshot to explain app/game features, make sure your text is on a clear background so it's easy to read it) keep text simple and clear like 'Catch Them All' or 'Great Icons' if your game doesn't has many features or options so make sure to add 2 screenshots only, if your game idea is clear enough - text is not must.
A good banner can help you when users share your app, this is the preview of your link, app name with a nice attractive background that relevant to the app/game is enough, try to explain the idea of the app in the banner so you can attract relevant users and not grab just clicks without downloads if the background is not enough for an explanation so you can add 3 main features of the app, for example:
* Download MP3 from youtube
* Order your MP3 songs
* Compress MP3 files
Remember the most important part is your icon because this is the first decision if to click on your app or not, make sure to invest on it much more time than the other things.
* Extra tip: A/B testing is a great way to test several icons/screenshots/banner designs and choose the best for you. google it for more information.