If you spend much time listening to sermons in the average American church, you will invariably hear a call for something which I call, "selfish service." Selfish service is when you are encouraged to serve others or God and the primary explanation given is a description of how serving others helps you.
For example, maybe you will hear a preacher mangle the book of Malachi, and encourage you to "put God to the test" in giving so that He will "shower you with blessings." The primary reason that you are told to obey (in this case, giving tithes and offerings) is because of what you will get out of it (showered with blessings).
Or maybe you will be told to serve and help others because that will make you more Christlike or it will bring God's blessing into your life.
Or maybe you will be told to support a certain ministry so that you can "be a partner with what Jesus is doing" on Earth.
Or maybe you will be told that you should serve at church because then God will one day say, "Well done, good and faithful servant."
In each case, the service you are being encouraged to give is reduced to a quid pro quo situation. It is no longer Christlike at all, for it is not sacrificial--you are giving in order to get: either blessings or peace or credit or God's pleasure. It changes the focus from the person who needs help to the person doing the helping.
But this is not what serving God is all about. We don't serve God to get something out of it: we serve God because He asked us to. We love others not because we wish for peace or blessing, but because God loved us and asks us to love others in the same way. He gave us Christ, and so we seek to become a type of Christ to those around us--serving others with no expectation of return.
I will give generously to my church, not to gain God's blessings, but because God asked me to generously support those who preach. I will serve in our youth ministry not because I will get some sense of satisfaction, but because I can help them. I will let God's wisdom guide me at work not because it will make me successful, but because that is what He asks me to do as His servant.
I think a lot of times we miss a little something about the concept of grace. The word charis, which the New Testament uses to describe God's love--predates Christianity. Charis--grace--was something which a patron gave to the needy. In return, the needy was expected not to try and repay the unearned gift, but rather to show loyalty to the patron and give him praise publicly. The client never tried to repay the grace, but he did try to reciprocate it by responding in loyalty. (This is why in the ancient Greek mythology, the Three Graces are shown holding hands in a circle: because as grace flows from the one giving it, so too does praise and loyalty return.)
You see, when I do it right, my service to God is about nothing other than an attempt to show Him loyalty. It is the emptying of me and the service of Him which is on my mind--not something I do to get blessings from Him. He asks us to participate in sacrificial, Christlike love--the taking up of our crosses each day--not because it will be good for me, but because it will be good for everyone. I give sacrificially not because it helps me, but because it helps those around me whom God loves.
Anything else and it is not service to God. So beware, preachers and parents: if you teach your flocks that they should serve others because of how God will bless them, then you have reduced His glory and grace to a financial transaction--give and get. And at that very moment, the service ceases to be Christian at all.