To start, you should know that the mobile gamers are quite different from the console gamers in several ways. This should be the first thing to consider before attempting to dive into the pool of mobile developers. More of this will be highlighted as I explain the topic in several steps.
1. The Platform.
This covers the OS you intend to develop for and it’s variations. Let’s take the iOS and the Android platforms for examples.
The iOS has little to think about when it comes to variations. If you develop an app for a generation of the iPhone, it can function on the same generation of the iPod Touch and latter generations.
However, this is not totally the same case on the Android platform. Here, we have to consider things like : the number of manufacturers and their variuos devices; the different screen resolutions of devices running on Android; the difference in GPU and CPU capabilities; and the global distribution of the various versions of Android.
2. The Limitations.
You have to consider the fact that mobile devices are not as powerful as game consoles and current PCs. Keeping this in mind will help you to optimize your app/game to run smoothly on mobile. You can get a video discussing this issue in details with this link ( http://vimeo.com/17919196) using the unity3d engine and Android as example.
3. Your Resources And Abilities.
Now, it’s time to think about your self. What is your level of programming? What are your artistic skills? Are you very good at innovating? Can you write good stories? Finally, do you have experience with other software relating to development (Photoshop , 3ds Max, etc.) ?
Also you need to think about how much you are willing to spend on development and marketing. I will advice that you are at least have experience with one software so you can at least understand a perspective of the work to be executed.
4. Development Software/ Engine.
You need to understand the interface of the software you are to use in development before you start deciding on what features your game should possess. This is quite critical because if you do not consider such, your game will not turn out to be what you wanted since you will have difficulties achieving what you set down.
5. Your Game.
Obviously, this is the main part. Your game should be immersive and quite addictive if you hope to make any income out of it. Your game should have a good presentation and be attractive at first sight.
We have discovered that on the mobile platform appearance can be more important than features. Nobody has the time to sample every app/game he finds until he gets a good one. Most mobile gamers respond to the visuals of your game. Remember that the first impression is most important.
If your game has some good game play features with poor graphics then you will have a hard time convincing people to try it out. The graphics will pull users to your game and the first stages/parts of your game will do the work of keeping them.
You also have to put in mind your market focus and the categories of people you are willing to reach out to. Are the people of that region willing to spend time or money on such?
Also, your marketing strategy is very important. If you fail here, then your whole work may be rendered futile. I advise you to make your game free and employ some other kind of monetizing strategy such as in-app purchases or ads.
With all these factors already considered and attended to, I can say you are set to begin development.