When Paul wrote to the Thessalonian believers he gave them credit for already doing the things he was encouraging them to do. In our Daily Verse Paul recognized they were practicing what he was teaching. His desire was that they would keep on doing it. It's neat to see a local church "get it" when it came to knowing what to do and doing it.
"Comforting each other" is another way of saying, "Help each other out by being there for them, listen to their concerns, let them know you care and do something practical that will lift some of the burdens they carry." Come alongside them and encourage them. If you're a Greek scholar you just noted that I described one of the great aspects of the Holy Spirit. In John 14:16 Jesus said He would "...give you another Comforter...." This refers to His promise of sending the Spirit of God to be the believers constant companion. The word "Comforter" used for the Holy Spirit is the same word used for "comfort" in our verse. It literally means, "come alongside side someone and help them."
Anyone you know today that could really benefit from that kind of action coming from you? Maybe you are the one who needs that comfort. You know what advice I want to give you? Go out and be a comfort to others. If no one reciprocates, you can be sure the Spirit of God will! He will always note your sacrifice of love for others. He "will not leave you comfortless", John 14:18 (KJV).