Righteousness???

W're discussing in class the ideas found in the Sermon on the Mount, specifically "righteousness" and the kingdom.

I'll begin the discussion with a question, posed to me by Kevin: What is righteousness?

Simply put, righteousness is what one ought to do, the righteous is the one who does what he ought. This may be a little over simplified though.

Romans 2:13
I John 3:17
Matthew 5:6

The issue flows quickly to "what ought I to do?" or to "what is God's will?"
So then, how do you determine God's will in specific situations and and in general? Beyond the pat answers of "read the Bible" and "pray", how do you do that? Fasting??? Confession??? Living in a community???

A related question...is righteousness "what one ought to do" different from one person to the next? Is it different for Christians and non-Christians?

Shoot me some thoughts.