How is a Christian baptized in the Spirit?
Biblically speaking, to be baptized in the Spirit is the same as believing in the Gospel of Jesus Christ. The experience of being baptized in the Spirit is also called being "born again." The saving work of the Spirit in the heart to bring faith is a spiritual baptism. Everyone who hears and believes the Gospel is baptized by the Holy Spirit in the sense that the Holy Spirit brought that person the capacity to believe and then indwelled that person from the moment of faith.
As Paul described it:
Rom. 8:14 For all who are being led by the Spirit of God, these are sons of God.
Rom. 8:15 For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, “Abba! Father!”
Rom. 8:16 The Spirit Himself testifies with our spirit that we are children of God,
We received the Spirit so that we would cry out to God (Abba, Father) and seek for His mercy. That moment is the moment we are saved, and it is the baptism of the Holy Spirit (or sometimes just called baptism).
Jesus taught this truth in John 3:
John 3:3 Jesus answered and said to him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.”
John 3:4 Nicodemus said to Him, “How can a man be born when he is old? He cannot enter a second time into his mother’s womb and be born, can he?”
John 3:5 Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit he cannot enter into the kingdom of God.
John 3:6 “ That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.
You can read more about the difference between water baptism and the baptism of the Spirit on our website.
On the other hand, those who teach of a supposed secondary "filling" of the Spirit are misinterpreting Scripture to arrive at a false view of the Spirit's work. You can learn more about the origins of these false teachings in our articles on Prayer Languages and Speaking in Tongues.