It came to pass after two years, that Pharaoh dreamed: and, behold! he stood by the Nile. And, behold! there came up out of the river seven good-looking and fat cows, and they fed in the reeds. And, behold! seven other cows came up after them out of the river, ugly and skinny, and stood by the other cows on the riverbank. The ugly and skinny cows ate up the seven good-looking and fat cows, and Pharaoh awoke. He slept and dreamed a second time, and, behold! seven sheaves grew on one stalk, lush and good. And, behold! seven sheaves, thin and blasted by the east wind, sprouted after them. The thin sheaves swallowed up the seven lush and full sheaves. And Pharaoh awoke, and, behold! it was a dream. (41:1-7)
The word "vehineh" ("and, behold") indicates the sudden appearance and recognition of something unexpected. It is therefore appropriate for dreams, in which events evolve spontaneously from one another with little concern for the rules of logic. Thus, every few words in the dream description, there is an "and behold!" to indicate that another random dream-image is appearing without rhyme or reason or predictability.
In fact, when "vehineh" appears multiple times within a few verses in the Torah, it is usually in the context of a dream. This is the case for Yaakov's ladder dream and Yosef's bowing down dreams, as well as Pharaoh's dreams here.
A similar case is brit bein habetarim, where God appears to Avraham in a "vision", and "vehineh" is used three times (verses 4, 12, 17) to describe his experiences. This "vision" is not quite a dream, since he is more or less awake for much of it, but it has the same unpredictability that dreams do. (At the risk of sounding flippant, I would say that Avraham here views the world as if under the influence of a psychedelic drug.)
The only other occasions in the Torah on which "and behold" is used repeatedly are in describing the appearance of tzaraat (Shemot 4:6-7, Vayikra 13-14, Bamidbar 12:10). What the connection is between tzaraat and dreams, I have no idea.
Pharaoh took off his signet ring from his hand, and put it upon Yosef's hand, and clothed him in fine-linen garments, and put the gold chain about his neck. (41:42)
What is "the" gold chain which Yosef now gets to wear? We see here and here that it was a very distinctive type of collar frequently worn by pharoahs. Perhaps it was therefore a symbol not only of wealth, but of royal authority, like the signet ring which Yosef received at the same time.
Interestingly, the striped coat which made Yosef's brothers jealous may have had the same purpose. It was quite possibly a symbol that Yaakov had chosen Yosef as the future leader of the 12 tribes. If so, then Yosef could have seen this as vindication of him and a sign that his dreams were finally beginning to come true.
The next morning he was troubled; and he sent and called for all the magicians of Egypt, and all of its wise men, and Pharaoh told them his dream; but none could interpret them to Pharaoh. (41:8)
Pharaoh speaks of a single dream, but the interpreters speak in the plural. It may be that Pharoah knew instinctively that the dreams had the same message, yet the interpreters insisted on interpreting them separately. The very first words of Yosef's interpretation are "Pharaoh's dream is one." Thus, intentionally or not, he immediately hits on the exact point that Pharaoh insisted on so strongly, against the opinion of all the magicians. This demonstrates either incredible skill or incredible luckiness (read: Divine providence) on Yosef's part. Pharaoh assumes the former, which is why he is then so enthusiastic about giving Yosef authority and power.