Quoting a piece of advice from Paul Eres on a post on Facebook’s Indie Game Developers group
There are only a few things you need to make money as an indie:
- Choose a genre that is selling, and that you enjoy playing and are good at.
- Be competent enough at programming and level design that you can make something that plays as well and is as fun, with some slight changes here and there to add your own personal touch based on your own desires and likes and dislikes.
- Either be an amazing artist, or have an amazing artist on the team, so you can make something that stands out graphically.
- Make sure either you can make a great trailer, or know someone who can, and make a trailer that stands out above all the other indies trying to make a game in that genre.
- Know some basics about marketing — know how to use your game’s trailer and screenshots to gather a following for your game before its release, so that a good portion of those interested in your genre know that your game will soon be released.
Note that being original and good at coming up with ideas is not in the list.