How can I pray about a decision? Or how will I know that I made a right choice? A good example would be should I stay with my old job or look for a new one? You see, I have a dream of becoming an ambassador someday, but I don't know if this is God's will for me.
Right and wrong are matters of God's law. Therefore, whether you are a farmer or a school teacher is not a right or wrong decision. Such a decision is a personal preference.
Let us suppose that you prefer to do something, and God decides that it isn't what He wants. Then the obvious answer is that it won't happen because things always go God's way. This is what Paul found when he wanted to preach in Asia. "Now when they had gone through Phrygia and the region of Galatia, they were forbidden by the Holy Spirit to preach the word in Asia" (Acts 16:6).
Most of the time, our choices won't make any difference. God will make use of us wherever we are.
So, if you want to be an ambassador, then go for it. If it works out, great! If it doesn't, know that you can still be an effective servant of God wherever you are and in whatever you do. "Therefore do not worry, saying, 'What shall we eat?' or 'What shall we drink?' or 'What shall we wear?' For after all these things the Gentiles seek. For your heavenly Father knows that you need all these things. But seek first the kingdom of God and His righteousness, and all these things shall be added to you. Therefore do not worry about tomorrow, for tomorrow will worry about its own things. Sufficient for the day is its own trouble" (Matthew 6:31-34).