How do you know if God is calling you to minister?

You will know if God is calling you when He has placed a heavy burden in your heart. I guess the follow-up question you would be asking is how would you know if such burden is from God? Well, there are two ways to find out. First is to allow time to test it. Do not make spur of the moment decisions and rush into the mission field or pastoral ministry. Take it seriously, pray hard for it and let time test its authenticity. Emotions, no matter how great, will pass or recede in months but a burden from God will never pass. Emotions weaken over time but a genuine burden from God will become worse throughout time. God's sovereign will for His people happens exactly as it is. The Bible also says that no one can run from the will of the Father. Jonah is a good example for this one. No one in Scripture was able to successfully evade the will of the God, not even His Son Jesus.

If your burden from God gets worse over the months, if you can't sleep well or you're constantly disturbed by it, continue praying and seek the counsel of godly men. There is a good chance that your distress is caused by God and He is truly calling you.

But if the heaviness of your heart, elation or distress ceases over the months, it is not really the will of God. It is possible that you were drawn by emotion. You must still be open to the possibility of God's calling. But at the moment, be assured that it is not or "not yet" His plan for you.

The same principle should be applied when your trying to find out if something is God's will for you. Pray, fast, seek counsel and give it time. The most important of these is prayer. Remain in constant communion with God.