First rule to serving is that it is more than just a Sunday role. Sure there are some important areas to serve in on Sunday (greeters, teachers, choir, usher, etc.) but service is a 7 day a week operation.
You have a gift! God has blessed you with talents and abilities. Some have more than others, but we all have something. These talents are orchestrated together within the local church to spread the gospel to a lost world and to reach out to those in need. Like a christmas present still wrapped up in faded paper what a waste it would be to have a gift and never use it.
You are needed! No one can do what God has designed you to do. Often in the life of the church we have to fill many roles and often some fill multiple roles, but God has made you unique and designed you to serve Him. 1 Corinthians 12:18-26
It takes one to reach one! We all tend to look at the "superstar" Christians and think "I'll never be of much use to God, look at how impressive (fill in the blank of popular christian) is!" The problem with that line of thinking is that so many in the church today were not saved by the superstar, but through the ministry of ordinary followers of Christ. There's someone out there who needs to hear the gospel that you have a connection to. They will see and understand it more clearly through you because of the way God has prepared you.