How do you know it's God?
There I some tests I use to help distinguish the leading of God's Spirit from my own desires or rationalizations or from other influences.
1. Is it consistent with Scripture? I find that Scripture bears consistent witness to God's desires and actions for humanity and that these dominant themes are outlined very well in Micah 6:8. "He has shown you, O man, what is good. And what does the Lord require of you? To act justly and to love mercy and to walk humbly with your God." So if the answer I seemed to get from God is just and kind and involves my humbly seeking to walk with and follow God, I tend to trust it. Obviously, it is easy for someone to lift out a few verses of Scripture and justify almost any position. But I find the overarching themes outlined in Micah to apply to the broad sweep of God's dealings with and desire for humanity and I tend to trust interpretations of Scripture that are about justice, lovingkindness and seeking God in humility.
2. Does this word or answer lead me to a place of peace? If God desires something of you, even something difficult, I find that you will have a sense of peace about it. That is not to say that we will always like what God asks of us. But if God is truly leading us down a difficult path, we will have the peace of God's presence with us on that journey and will know that God has prepared us and has prepared the way for us. Paul prayed several times to be delivered from his "thorn in the flesh." But ultimately he learned to deal with it and to acknowledge that God's grace was sufficient to get him through. God doesn't promise us an easy life. But God promises to go with us each step of the way and that even the most awful things that happen to us can be used for good if we love God and are called according to his purpose. Just don't let that position be used to let someone use you as a doormat. There is a difference between being willing to be poured out for God's kingdom purposes of healing and allowing ourselves to be abused for no good reason.
3. Does God's community bear witness to the truth of the message you have received? Notice I didn't say "Does your church agree with you?" Jesus, the disciples, countless saints and martyrs, and voices of dissent such as Martin Luther, Bonhoeffer, and Martin Luther King all found themselves on the wrong side of religious authorities from time to time. But the beloved community, the true Christian witnesses, stood against narrow interpretations of religion that kept people in oppression and that used God to force people into molds that denied the shape God would have them take. If what you hear from God bears witness with the faithful throughout the ages and speaks to the freedom Christ offers from narrow, negative religion, then it is probably trustworthy.
4. Does this idea you think is from God harm other people? When Pastor Jim Jones thought God was telling him to poison his flock with bad Koolaid, that idea was not consistent with Scripture or the witness of the Community of God. And, sick as he was, I doubt it brought him any peace. If the Lord who allowed himself to be broken knowing that our wholeness would be the result tells us to turn the other cheek rather than strike back at others, I think he meant it.
Despite the bloody history of people killing other people in the name of God, I don't believe God calls us to harm each other. Notice that prior to the flood in the Genesis account, even the killing of animals was not allowed. Surely God doesn't mean for us to kill or harm one another in God's name.
These are just a few ways of seeking to know if the voice we hear is trustworthy and of God. We need to test our notions of God's will for our lives against Scripture and community, discerning if our ideas are consistent with the loving and giving God who chooses to give us grace rather than the hard justice we sinful folk deserve. If the little voice tells us to offer grace to one another, there's a pretty good chance God is behind the voice.