How to know if it is God speaking

"Passport: A Believer's Guide to the Kingdom of God" has a great checklist on pp. 36-37 on how to know if a voice that you're hearing is God speaking:

1. The voice of the Lord always agrees with Scripture.
2. You sense the thoughts are coming from your 'inner being', not just your mind or emotions.
3. The thoughts given by the Holy Spirit are often unlike your own ideas and sometimes have a 'that's not like me' quality. God may surprise you with a word that is not what you would have expected.
4. The word of the Lord comes with a sense of peace -- even the ones you don't like. When a thought stirs up fear, doubt, despair, confusion or anxiety, it is usually not the Lord. Those things are the devil's tools, not God's.
5. It brings God glory, not you.
6. Just because you want something does not make it wrong, but be careful about things where you have strong feelings. When I have strong feelings about an issue, I look for guidance from the counsel of Christian friends who are more neutral. Be careful about romance issues in particular.
7. Sometimes I know it is God speaking because I react with irritated anger. He is telling me the one thing to which I do not want to listen (but need to) and I get annoyed (see #3).