The traditional way in which any Israelite was to be saved, was to first repent (and be baptized) as evidenced in both the preaching of John the Baptist (Mark 1:4,15) and that of Peter (Acts 2:38; 3:19.) It appears that this repentance was intended for "the remission of sins" and to "believe the gospel"... which at the time simply meant, believing that Jesus was the Christ (i.e., the promised Messiah), the son of the Living God. Peter's words in Acts 2:38 seem to indicate that it was subsequent to this that one would then "receive the gift of holy spirit."
However, it appears that this isn't exactly the same path or course of salvation that Paul (who refers to himself as the apostle to the Gentiles in Romans 11:13, and a teacher of the Gentiles in both of his epistles to Timothy) later preached with his gospel. This probably shouldn't be surprising, considering that the gentile nations were not given the same promise of a Messiah, nor were they given a way or any means for the remission of sins. Perhaps this is why the focus of Paul's message is first and foremost on the acceptance and belief in the death and resurrection of Christ, rather than on a change of heart and the remission of sins... which both appear to occur only AFTER believing in the resurrection of the dead, and receiving the free gift of righteousness. (Romans 2:4.)
Plainly speaking, the baptism of John (and perhaps that spoken of in Acts 9:18) was by or with water. However, there is also a baptism by or with spirit (as spoken of in 1Cor.12:3)... which Paul also seems to refer to as being Christ in you (2Cor. 13:5; Col. 1:27.) Furthermore, it appears that Paul also states that this may have been revealed to him while on the road to Damascus.
 But when it pleased God, who separated me from my mother's womb, and called me by his grace,  To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:
So... this question remains. When, and by what sequence of events, was Paul actually saved?
Evidently this is not as easy a question to answer as some of you might think.
To draw more attention to this, I considered putting a bounty on it (even though I haven't been at this site long to earn many points.) However, the difficulty that arises in pinpointing a scriptural answer to this question raises another, perhaps far more interesting question which I will pose that links back to this question.