God's mandate.
He WANTS US TO. Consider it. Have you truly considered what God is doing around the world, even in your own neighbourhood, and [how] you can join in?

God calls us all to missions.
Whether it be globally, or locally, God wants to use every one of us. That includes you.

There is an aspect of the Christian life that many people leave out, and it's service. God trains us to be servants. God wants us to be transformed for every good work, and that is done by the refining of his word. "All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work." [2 Timothy 3:16-17]. If we aren't seeking to serve God, our Christian life will become dull, boring, and the little of the life we have will eventually fade away. Serving God is where it's at, and when you find yourself serving God, you'll find that God will be drawing you closer to himself.

So where do you start?
God's mandate; remember it, because it's the most important part of it all. Serving God isn't doing something for God out of your own initiative, it's out of God's intiative. Simply put, it's the difference between saying, "Lord, I am going to do this" and "Lord, use me in any way." You can start by letting God transform your life for mission work. Wherever you go, God wants to use you, that's a gaurantee. So in order for God to be able to use you in the greatest way, you need to be refined according to the word. If you don't feel suitable for any sort of mission, don't fret, God can still use you. He'll take you as you are, and use you as you are. However, God wants you to be more like him, reflecting his glory, and making an even bigger impact - so expect a change in your life.

What did Jesus say?
We are the salt and light of the world. (Matthew5:13-16). Do you know what that means? Let it sink in, because that's the basis of what we do, that's the basis of who we are. As Christians, we're automatically different from this world, so don't bother being the same as your non-christian neighbor in what you do, but be different. At the same time, relate to the non-christians you meet in any way you can, relationships make sharing the Gospel more effective. But draw the line, don't let being 'relational' with non-christians pull you away from following God's will.

Let God use you. Let God know that you want him to use you, in whatever way possible. When you do this, you can expect that God will want start letting you see the opportunities. Take those opportunities, don't let Satan steal them.

What about your comfort zone?
One thing is definite, you won't be needing your comfort zone any more. You might as well ignore it. It's no use to you, and it's no use to God. If you have any sort of fear, any doubts, or anything else that is preventing you from letting someone know the Gospel, it is guaranteed that it isn't from God. What you can do in this type of situation, is either willfully ignore it and go ahead with the plans (good idea), or you can pray and let God strengthen you and give you courage (recommended), and you can always memorize scripture to fight the lies. "...If God is for us, who can be against us?" (Romans 8:31). Use verses like that to combat with the lies that arise from stepping out of your comfort zone. Whatever you do, be strong, God is with you.

"Be strong and courageous, do not be afraid or tremble at them, for the LORD your God is the one who goes with you. He will not fail you or forsake you." [Deut 31:6]