Your game icon is the first impression. It has to pop out from the rest, grab attention and fascinate. Experiment early with different concepts. Post these on Facebook or on your community forums to get feedback.
Show your game from its most exiting side. Show the action. Don't bother with title screens, menus or game over scenes.
Do not rush your game once the coding is done. Look at it again and add every bit of extra gloss and tactile feedback you can.
More particles, more bounce in the buttons will sell your game.
It is much easier to get noticed in small countries. The audience is usually keen on trying a game if the app description is localized in the native tongue. If you manage to get good traction in a small country, the chances are good that the popularity will spill over to other countries. Also, a feature placement on a small app store will often attract the attention of the stores in larger countries.
Build a relationship with streamers and YouTube channels. Even small channels can get virality started. Be represented where ever you can.
Join forums on gaming and game review sites. Be present, comment and make a name for yourself even before you need to market your own game. Once you are ready to show your game, you will already be recognized and more likely to draw attention to your game.
Reach out to journalists. Make sure you have a professional press kit ready. There are many online resources which can help. Send personalized emails to journalists and choose a subject that will peak their interest.
Once you have established a report with a journalist, stay in touch. Keep them informed of updates. Keeping the relationship going will pay off when you release your next game.