"We believe in the Holy Spirit"

He has often been referred to as "the forgotten God," but while it is possible there may have been a "Christianity" without the Holy Spirit, there would certainly have been no Christians. As the third Person of the Triune God, the saints of old recognized and emphasized the vital role the Holy Spirit plays in the present age as the Lord and Giver of all spiritual life. How do Christians today think about Him? How should we?