First Comforter, Prophecy as Hallmark

"This first Comforter or Holy Ghost has no other effect than pure intelligence. It is more powerful in expanding the mind, enlightening the understanding, and storing the intellect with present knowledge..." (Joseph Smith, HC 3:25, p. 380)

"Therefore it is given to abide in you; the record of heaven; the Comforter; the peaceable things of immortal glory; the truth of all things; that which quickeneth all things, which maketh alive all things; that which knoweth all things, and hath all power according to wisdom, mercy, truth, justice, and judgment." (Moses 6:61)

The Holy Ghost fell upon Joseph and Oliver and stayed with them after being baptized only:

"Immediately on our coming up out of the water after we had been baptized, we experienced great and glorious blessings from our Heavenly Father. No sooner had I baptized Oliver Cowdery, than the Holy Ghost fell upon him, and he stood up and prophesied many things which should shortly come to pass. And again, so soon as I had been baptized by him, I also had the spirit of prophecy, when, standing up, I prophesied concerning the rise of this Church, and many other things connected with the Church, and this generation of the children of men. We were filled with the Holy Ghost, and rejoiced in the God of our salvation. 

"Our minds being now enlightened, we began to have the scriptures laid open to our understandings, and the true meaning and intention of their more mysterious passages revealed unto us in a manner which we never could attain to previously, nor ever before had thought of." (JSH 1:73-74)

"And the Spirit shall be given unto you by the prayer of faith; and if ye receive not the Spirit ye shall not teach....And as ye shall lift up your voices by the Comforter, ye shall speak and prophesy as seemeth me good;  For, behold, the Comforter knoweth all things, and beareth record of the Father and of the Son." (D&C 42:14, 16-17)

The Holy Ghost removes carnal desires, replaces with desire to do good.

Faith comes by hearing the word of God.  (This presupposes the speaker is in possesion of it, or in other words, is speaking by the power of the Holy Ghost)

Gift of prophecy is the hallmark of having the Holy Ghost.

"And they all cried with one voice, saying: Yea, we believe all the words which thou hast spoken unto us; and also, we know of their surety and truth, because of the Spirit of the Lord Omnipotent, which has wrought a mighty change in us, or in our hearts, that we have no more disposition to do evil, but to do good continually.

"And we, ourselves, also, through the infinite goodness of God, and the manifestations of his Spirit, have great views of that which is to come; and were it expedient, we could prophesy of all things.

"And it is the faith which we have had on the things which our king has spoken unto us that has brought us to this great knowledge, whereby we do rejoice with such exceedingly great joy." (King Benjamin, Mosiah 5:2-4)

"No man can receive the Holy Ghost without receiving revelations. The Holy Ghost is a revelator." (Joseph Smith, HC 6:3, p. 58)