A casual Christian has an interest in Jesus but is not dedicated to him. Casual Christians focus more on themselves than Jesus. Casual Christians will not make hard decisions, usually involving how they spend their money, to better follow Jesus. Instead, they reason that Jesus just wants to know they'd be willing to do it.
You might be a casual Christian depending on how you answer these questions:
1. Do you attend worship because you think you're commanded to or because you want to worship God and remember Jesus?
2. Do you read the bible for information or for transformation?
3. Do you act upon what you learn or do you file it away as a nice insight to do something with "later"?
4. Do you pray?
5. Do you view spiritual growth in terms of becoming a better bible reader or church attender or in terms of conforming your life more and more to the image of Jesus?
6. Do you spend time with other Jesus-followers?