Speaking in tongues is not the only sign that a person has been baptized in the Holy Spirit. When Jesus told the disciples that he was going to baptize them in the Holy Spirit he didn’t even mention tongues.
Instead, he focused on the fact that this was preparation for their ministry. He said that they would receive power to witness to Jesus Christ throughout the world (Luke 24:49, Acts 1:8). One sign that the early believers were baptized in the Holy Spirit must indeed be that “they spoke the word of God boldly” (Acts 4:31).
Another indicator of Spirit baptism was that, “The apostles performed many signs and wonders among the people” (Acts 5:12). The apostles also received guidance from the Spirit (Acts 16:10).
Another sign that a person had been baptized in the Spirit was that they would overflow with praise to God (Acts 10:46). Dreams, visions, and prophecy were also indicators that one had been baptized in the Holy Spirit (Acts 2:17).
The long discourse on the unity of the church, which occurs in Acts 2:42-47 directly after the story of Pentecost, indicates that church unity was also a sign that people were baptized in the Holy Spirit.
Considering the biblical emphasis on the relationship between the Spirit and love (consider Rom 5:5 and 1 Cor 13), William J. Seymour, leader of the Azusa Street Revival, viewed love as the key sign of Spirit baptism. He wrote that if your life did not “measure with the fruits of the Spirit…you have not the baptism with the Holy Spirit.”
In light of all of the above, it would be fair to say that there are many signs of the baptism in the Holy Spirit.
For those who might be wondering, my credentials are secure :). The section in the PAOC Statement of Fundamental and Essential Truths on Baptism in the Holy Spirit (5.6.3) mentions numerous signs of Spirit baptism (although not specifically using the term ‘sign’). And these signs are listed even before any mention of speaking in tongues.
Specifically, the statement affirms that through baptism in the Holy Spirit a person “comes to know Christ in a more intimate way and receives power to witness and grow spiritually.”
Pentecostals frequently teach that speaking in tongues is the initial evidence that a person has experienced the baptism in the Holy Spirit, but this does not mean that there are no other indicators that should be found after this initial evidence. Hence, D. W. Kerr, a leader in writing the Assemblies of God (USA) Statement of Fundamental Truths, wrote that, “We can consistently say that ‘tongues are not the only sign of the baptism,’ and yet be just as consistent in saying that ‘tongues are the sign of the baptism.’”
Similarly, James E. Purdie (founding principal of the first PAOC Bible College), wrote that evidences of the infilling of the Holy Spirit include “a much greater passion for souls; a greater reverence for the Word of God, and a greater love toward all true Christian people, as well as the deepening of the prayer life . . . [and a person’s] earnestness to help others.”
My concern is that too many Pentecostals have made Spirit baptism only about speaking in tongues. Although I regularly experience the value of speaking in tongues, I appreciate the words of Minnie Abrams (Pentecostal missionary in India), who wrote in 1911, “When I see anybody seeking to speak in tongues rather than seeking the power to save souls I am grieved.”
It worries me that so many Pentecostal sermons on the baptism in the Holy Spirit focus so extensively on speaking in tongues. These sermons often concentrate on proving that if you are baptized in the Spirit, you will speak in tongues, and then proceed to an altar call with the preface, “this is how you speak in tongues.”
I am concerned because Spirit baptism is not just about speaking in tongues and because presenting Spirit baptism in this manner makes Spirit baptism all about personal experience (“do you have it?”), or, even worse, we can present Spirit baptism as only a one-time personal experience.
In our preaching, let us not neglect the numerous signs that should follow Spirit baptism and the personal responsibility to utilize the anointing of Spirit baptism for ministry by keeping in step with the Spirit.
See also the Assemblies of God (USA) position paper, “Baptism in the Holy Spirit: The Initial Experience and Continuing Evidences of the Spirit-Filled Life”
 William J. Seymour, “To the Baptized Saints,” Apostolic Faith (Los Angeles), 1:9, June-September 1907, 2.1.
 D. W. Kerr, “‘The,’ ‘A,’ or ‘An’—Which?” Pentecostal Evangel (21 January 1922), p. 7.
 Cited in Peter Althouse, “The Ecumenical Significance of Canadian Pentecostalism,” in Winds from the North: Canadian Contributions to the Pentecostal Movement, ed. Michael Wilkinson and Peter Althouse (Leiden: Brill, 2010), 72.
 Minnie F. Abrahms, “The Object of the Baptism in the Holy Spirit,” Latter Rain Evangel (May 1911), 10.