We started a study Sunday on the parables and mysteries of the Bible.  The first parable of Jesus was the one of the sower who sowed among different soils.  I've heard preachers use this to describe different kinds of Christians, but I believe the seed is the word of the kingdom (i.e. the gospel) and the ones who produce fruit are true believers.  It's easy for us to look at outward appearances--a quick decision to follow the Lord, spiritual excitement or shedding of tears--but the proof that God's word has found a place to live, grow and thrive is when genuine fruit is produced.  Jesus was teaching at a time when religious leaders all around Him were claiming to be the real deal, but were in truth lovers of money, proud and murderous.  Their lack of fruit, despite their religious reputation, showed that God's word had never taken root in their lives.  Others like the rich young ruler, Nicodemus or the parents of the blind man healed in John chapter nine, knew the truth--even believed it--but would not follow Christ because of the cost to their reputations.  What I'm saying is that the only way to know for sure is by a daily walking in right relationship to God in which His Spirit in us is consistently bearing good fruit.  We don't need to settle for religious experiences or charismatic euphoria.  We need to walk with God and allow His working in us to give us all the assurance we need that we are His forever.