I often make it a practice to familiarize myself with a book of the Bible by reading and saturating myself in it for 30 days in a row. I find this incredibly helpful. If the book is too long to read in one sitting, then I divide it into sections, reading each for 30 days.

Currently I am reading through the Paul's Epistle to the Philippians and ran across some good material that I wanted to share with anyone who will listen.

In chapter 3 of this book Paul gives us one of the best definitions of a Christian available in the Bible. He also contrasts this with the marks of false teachers.

Paul begins the chapter with the wondrous gift of grace with the hopeless pit of sin. He warns the Philippians against false teachers; those, he says, who have confidence in themselves. That is, anyone who adds conditions for salvation in addition to the grace of our Lord Jesus Christ. Paul likens to Gentile dogs, those who fail to recognize that salvation is wholly of Jesus.

But then in stark contrast to false teaching, Paul defines what a Christian looks like. He calls true Christians "the real circumcision", i.e. the true covenant people of God. There are three characteristics Paul gives of Christians found in verse 3. He says they are those who:

1) Worship in the Spirit of God
2) Glory in Christ
3) And put no confidence in the flesh

(1) The first mark of a Christian is that they are those who worship in the Spirit. They are the true circumcision, Paul says. They do not worship in the flesh. The "flesh" here is not referring to our physical bodies, for there is nothing inherently wrong with physicality. What Paul is referring to is human effort or trust in ancestry - trusting in it for our redemption. Worship in the Spirit of God also means that the source of our life and walk in Christ is the Holy Spirit who unites us to Jesus Christ. "It is the Spirit who gives life; the flesh counts for nothing." (John 6:63) Gal 5:25 likewise says, "If we live by the Spirit, let us also walk by the Spirit." Thus both our conversion and our sanctification can be attributed to the work of Christ applied by the Spirit.

(2) Christians are also defined as those who "glory in Christ" are those who have no hope save in Christ Jesus. The mark of a Christian here, Paul says, is that they glory in Christ, that is, give our weight to Him, not anything else. To glory in someone one must have affection, desire and are driven by that someone. Christ is the one they will cherish above all. Of course this is a constant struggle even for a Christian. There is a constant heavy pull in the world to glory in ourselves or in something else, but the Spirit who lives in us preserves us. We think we can find ourselves in something less than the real thing and so we disbelieve God's promises. But the Holy Spirit uses such instances to discipline us as children to draw us nearer to Himself.

(3) Lastly a true Christian is one who has "no confidence in the flesh". This means they have utterly dispaired of themselves. When the Holy Spirit does a work of grace in someone, He convicts them of their sin. Not just sins, but convicts of the fact that they are sinners by nature and can do nothing to save themselves. There is no pride in physical decent or in natural abilities. This means one who is brought to faith, repents of both their good works and their evil works. Both are equally worthless to God. False teaching glories in something other than in Christ alone, always pointing to something that we can do; a resumé we can bring before God to curry His favor, not realizing that He has already adopted us as sons. Not unlike the older brother in the Prodigal son who glories that he has worked for his father all his life, not realizing that God does not first ask us to meet conditions to obtain his love. Those who have confidence in the flesh also tend to believe in Christ PLUS this or that. That Christ saved them, but they must maintain their justification before God. Glorying in Christ is the antithesis of glorying in the flesh. Pharisees boast before God of what they have done for him. The Christian is one who has empty hands every day and can only thank God for His mercy. He thus relies solely on the righteousness of Christ.

It is the new Covenant in Christ's blood which "reminds God" not to treat us as our sins deserve. True Christians flee to Christ as their only hope. A mark of maturity is that we no longer are constantly worrying about our own spirituality but rather our focus is on Christ and His accomplishments. Those who are glorying the flesh will exhaust themselves because they are looking to their own resources. The cross is where we find sanctification. Christians flee to Christ as their only hope casting aside all self-confidence and autonomy. Paul calls everything other than Christ "rubbish". Are we trusting in rubbish or in Christ? A.W. Pink, I believe captures the point in a sentence:

"Just as the sinner's despair of any hope from himself is the first prerequisite of a sound conversion, so the loss of all confidence in himself is the first essential in the believer's growth in grace."

http://www.reformationtheology.com/2005/10/pauls_definition_of_a_christia.php