Matthew 28:19-20 (KJV) Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
Following the commandments of God is what can make us true disciples. A disciple is one who obeys the doctrines of Jesus Christ. When we follow all the commandments of God that is what will make us disciples of Jesus Christ. It is the commandments that make a person a disciple.
John 8:31 (KJV) Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed;
Being in the church of God does not make a person the disciple of Jesus Christ. Anyone can choose to belong to any sect which he or she chooses. If we want to be the disciples of Jesus Christ, the beginning of it is that we have to believe in Him and then choose to be followers of His doctrines. There is no difference between a person who does not join the church and the one who only comes to the church without obeying the commandments of God.
2 Timothy 2:19 (KJV) Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity.
The Bible says that God knows those who are his own. He knows them because they are obedient to His teachings. He said: my sheep hears my voice, a stranger will they not follow. So if you actually are His sheep, you will follow his commandments.
John 10:5, 27 (KJV) And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.
My sheep hear my voice, and I know them, and they follow me: