The thief on the cross at the same time Jesus was on the cross, received salvation right there on the spot. How was he able to do this without a water baptism in Jesus name or a Holy Ghost baptism?
 
The new testament covenant was not in effect yet. Jesus had not yet been glorified; he was still alive when he granted the thief salvation. The new testament covenant went into effect on the day of Pentecost; the day that the promise of the Father (The Holy Ghost) was given in the upper room. This was some 50+ days later after that day of the cross.
 
Secondly, I believe that repentance/belief/faith is what saved the thief. I am not familiar with what was in place for salvation during this time, but I'm certain the new testament was not in force.
 
This question/topic comes up quite a bit and I truly hope this helps many.
 
God Bless!
Kent