A while back I got to my gate in the Detroit airport, and J. I. Packer was sitting there waiting for the same flight. I asked him questions, and he patiently answered them. His parting word to me: emphasize the doctrine of the Trinity in every aspect of my ministry as pastor and theologian. Not sure what I was expecting, but at the time Dr Packer's answer surprised me. Since then I've become acquainted with the writings of John Owen (1616-83), Packers' mentor in the Great Tradition and by most accounts the greatest Puritan theologian. They're incredible, and a big part of why that's so is that Owen exemplifies what Packer commended to me. For example, here's Owen summing up the gospel in his big book on the Holy Spirit: 

"When God designed the great and glorious work of recovering fallen man and the saving of sinners, to the praise of the glory of his grace, he appointed, in his infinite wisdom, two great means thereof. The one was the giving of his Son for them, and the other was the giving of his Spirit unto them. And hereby was way made for the manifestation of the whole blessed Trinity; which is the utmost end of all the works of God. Hereby were the love, grace, and wisdom of the Father, in the design and projection of the whole; the love, grace, and condescension of the Son, in the execution, purchase, and procurement of grace and salvation for sinners; with the love, grace, and power of the Holy Spirit, in the effectual application of all unto the souls of men - made gloriously conspicuous."