Colossians 3:16 is not a suggestion. Rather it is a command to let the Word of Christ dwell in us, and not just dwell but dwell richly. It is to be the basis for our speech to one another: speaking in Psalms and hymns and spiritual songs...how do we do this if the Word is not actually in us. And how is it in us? What does this mean practically?
How many of us can close our eyes and meditate on a passage of scripture because it is in our hearts? And yet in passage after passage in the Old and New Testaments this is exactly what we are told to do. Think about this statement of Jesus: He who has my commandments and keeps them, he it is who loves me...John 14:21
One of those very clear commands is to hide God's word in our hearts, to mediate, ruminate, discuss and let it permeate our lives and inform our every decision. see Joshua 1:8, Deuteronomy 6:6-7, Psalm 1, Psalm 119:97-105 and many more). How do we abide in Him and have Him abide in us without knowing His word? It seems to be the core basis of our spiritual lives? And yet we ignore it in practice.
I don't mean this in a legalistic, rote sense. The one who knows the most verses may be the least spiritual. I ahve heard all the arguments: "knowledge puffeth up"etc. Yet the commands are there over and over. We are disobedient if we are not hiding God's word in our hearts.
One of the foremost authorities on spiritual growth today is Dallas Willard. He calls Bible memorization the #1 most important spiritual discipline over even prayer. Often the scripture in our hearts is the basis for our prayers.
If we love Him we should love His revealed word and want to thoroughly learn it so as to grow closer and closer to Him. I challenge you to start now. Don't wait. Choose and passage and begin to learn it...and meditate on it. And ask God to open it up and apply it to your life.