In the book of Acts, the apostles were baptized in the Holy Spirit after they already believed in Jesus Christ. Some churches have taken this to mean that being saved is a two-step process. What they forget is that the apostles were living in a unique time; the transition time between when Jesus ascended and sent the Spirit in His place to be with us on Earth. Since the event itself was a two-stage process, anyone living during that time would have experienecd it in this way. All believers after this era, however, receive the Holy Spirit at once, as they already live in the time of the Spirit. There is no need to wait for the Holy Spirit to come down from heaven and fill the new believer. He is already here.