Opinions abound.
However, scripture provides a direct answer as to how New Testament believers become born again. Every detailed account includes belief in Jesus, repentance, water baptism in the name of Jesus for remission of sin, and receiving the the gift of the Holy Ghost. (Acts 2:4-41, 8:12-18, 9:17-18, 10:43-48, 19:1-7, 22:16) Being birthed into the body of Christ remains the same for people today as it did for those present at Pentecost. The same foundation must be laid by all as revealed throughout scripture, particularly in Hebrews 6:1-2. Afterward, the believer who has become born again is to pursue a lifestyle that promotes becoming Christlike. This is only possible through accepting principles found in the word, and being led into all truth by the indwelling presence of the Holy Ghost. The Apostle Paul said, I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway. He also said everyone is to work out their own salvation with fear and trembling.
Jude instructs us, "Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith (seek out) which was once delivered unto the saints.
Salvation is by grace THROUGH faith. Faith in what God says is true and obedience as He instructs.
Again, some of the Acts accounts you cited report that believers WERE WB, but not that they were damned if they DIDN'T get WB,
whereas Acts 16:31 and Paul's epistles (Rom 3:21-22, 1Cor. 1:17, 2Cor. 5:7, 13:5, Gal. 1:6-9, 2:16, Eph. 2:8-10, Phil. 1:29, 2:9-11,
Col. 1:3-4, 2:16-17, 1Thes. 1:2-8, 3:6-8, 2Thes. 1:3-4, 2:13-14, 1Tim. 1:3-7, 4:1 & 10, 6:11-12, 2Tim. 1:5, 2:22-26, Tit. 1:1 & 10, 2:1-2, 3:4-7, Philemon 1:4-5, Heb. 3:12-19) teach that BElIEF/SB is essential for salvation, NOT the work of WB.