On Sunday I preached on God-Centered evangelism. I encourage you to listen to (or read) this sermon on our website and consider how God wants to use you in your sphere of influence. It's so encouraging to know that God will be faithful to accomplish His purposes, and we have the great privilege of watching Him work!
I also want to direct you to a sermon by John Piper that has been very encouraging to me.
You can find it here.
It's also available in Spanish here.