Mobile games has become a huge success over the last few years and while there is no doubt that some are immensely more popular than others, there are still tons out there do very well for themselves. To make your mobile game a success though you'll have to start considering ways to monetize it, and this should be a series of steps you go over before the game is published as you want to have a plan in order. There are more than a few app monetization models which you can utilize to your advantage, but it can be a little daunting sometimes to figure out which ones may be best suited to the type of game you're trying to build and develop. If you're not sure where to start, we've put together some suggestions here which can help you move in the right direction.
Perhaps you expected it, and perhaps you didn't, but advertising can and probably should be a big part of how you monetize your game. There are lots of different ways to advertise which is what makes this a good step in the process. You don't necessarily have to employ every single advertising tactic, but dipping a toe in the waters of more than a few can't hurt as long as you can handle the costs associated with them. As stated there are many different types of advertising you can employ, like banner ads in games, ad views when exiting games, and you could even cross promote with larger gaming publishers by inserting ads for other people's games which may be related to yours or that you feel the gamer may find interesting. You can also give gamers incentivized ads like coupon offers which are usually other companies ads who you could receive payment from to insert them into your game, or video ads which players can watch to obtain in-game content and items to use while playing. Some advertisers may even pay you to visualize their brand onto in-game items to gain their brand more exposure to people.
Advertising, of course, isn't the only way to monetize, and if your game is free you may want to explore the realm of utilizing freemium content, like selling DLC packs for extra game content like levels, or in-game items such as coins or other premium currency used to buy in-game items and gear, or even gear itself. You could also monetize things like experience boosts and weapon enhancements if your game is the type that makes use of a leveling system with characters who can equip weapons. There's also the option of giving people a free trial version of a game, or a free version of your game that's ad-supported. Using this method, you can offer a premium version of the game to those that may want to get rid of ads or may want to upgrade to the full game and continue playing the content. This gives players two options, those who would rather play for free, and those who would happily pay up to get rid of ads or experience the full game.
You could also impose game limits and/or a virtual economy. Limits could be things like players paying for more time to complete in-game levels or achievements, or paying to speed up a timed process like upgrading a vehicle or building a new structure for your base. Supercell employs this tactic for Clash of Clans, allowing players to build new structures at a fraction of the time by purchasing premium currency used to speed up the process. When it comes to virtual economy, there are a good number of different options available here. Anything from new characters to character/avatar customization to in-game boosts or items could fall into this category. You could also utilize things like seasonal items, an option to pay for currency (such as gems) to bring someone back to life and continue from the point they lose, (plenty of endless runners will utilize this tactic so players have an option to continue without restarting the level - see Bulypix's most recent game Yurei Ninja as an example, which lets players continue from the same point which they lose at if they pay to revive. Reviving each time will cost a certain amount of Sakura, which can be purchased in varied amounts for different prices starting at $1.99) or you could charge for resources, something which is commonly seen in building/strategy games like Clash of Clans and others.
If your game becomes big enough, a way to gain additional monetization is through merchandising and selling of physical products like T-Shirts, toys, and the like which can be very lucrative if your game has a huge following of dedicated fans. You might also want to consider various forms of billing like vouchers or wallet payments, both of which could be used for people to pay for items or currency outside of the game which could be used for your game. If nothing else, bringing social aspects into the mix by allowing players to gift items to each other.While there are likely many more methods of how you can monetize your mobile game, hopefully some of these tips have helped to spark some ideas.