Teaching How to Speak in Tongues?

This is a continuation of this most recent post, and this post; see 1 Corinthians 12–14 for reference. Obviously the issues of speaking in tongues, prophecy, miracles, signs, and wonders are still some of the foremost on my mind.

As I read through Charismatic Chaos (MacArthur, 1992 edition) and compare the information therein with what's in the Bible in 1 Corinthians, Acts, and related passages, I'm astonished at what some people today believe about signs, wonders, miracles, gifts of the Spirit, prophecy, and speaking in tongues. My latest thought, which now I must explore, is this: If speaking in tongues is a gift from the Holy Spirit (a few others are prophecy [edifying, or building up, the church], teaching, encouragement, giving, leadership, mercy [Romans 12:3–8], wisdom, the word of knowledge, faith, discerning of spirits [1 Corinthians 12], speaking, and ministering [1 Peter 4]). Some of these gifts are still in use today. Some have ceased or will be done away (1 Corinthians 13).

Specifically, "whether there are tongues, they will cease." Tongues, or speaking in pagan languages that no one understood, were a sign to unbelievers in the time of the apostles. This sign verified the apostles' testimony and proved to those who would otherwise not have understood that GOD IS GOD. Now that we have the complete canon, or Scriptures, that explain to us who God is and reveal that He sent Jesus, His perfect Son, to earth to die on the cross and forgive us of our sins if we accept this free gift from Him, we do not have need to the temporary, verification sign of speaking in tongues.

And yet there are those who believe that the Bible says that they can still be used today. So there are classes and workbooks and seminars that teach those who want to learn how to speak in tongues. so I ask:

If speaking tongues is indeed a valid gift of the Holy Spirit, still in use today, why then do we need to be taught how to do so? (The same goes for prophecy in the sense of revelatory oracles, not in the sense of edifying the church.)