All the signs and wonders and speaking in tongues in Jerusalem that day were preparing hearts for hearing of the Word of God. And when Peter gets up to preach, he goes back to the Scriptures. In quoting Joel, the point is made clear that the message of God about Jesus is for all people, "all flesh" regardless of distinctions (like national, social, sexual, ceremonial, or educational/intellectual). "Calling on the name of the Lord" glorifies God because it forces us to admit our great need and to look to the only One qualified to rescue us - Jesus Christ. Christian - since you've been filled with His Spirit, you have been commissioned and empowered by the Spirit to tell of the mighty works of God to the world for His glory.