Upvote:9
As mentioned over in this answer, they're not regarded higher or lower than the others, since they are all the word of God. Everyone's individual experience will vary with which scriptures are emphasized. Usually, the Book of Mormon and Bible are read from most often.
The Doctrine & Covenants are mentioned for a more recent, historical account of God's revelations and on matters of things that are not clearly covered already in ancient scripture. The Pearl of Great Price is probably least often cited, but contains important clarifications and expansion of some of the events in Genesis, Joseph Smith's personal history, and a better account of Matthew 23-24. Not because it's least important, but because it's the smallest book.
The Book of Mormon is probably the most practical to apply in one's life since it is the only canonized book of LDS scripture which was written not only as a historial record like the others, but the authors of the Book of Mormon indicate they saw our day and wrote their record for us in our time.
Upvote:14
Because Mormons believe in an open canon of scripture (i.e., that God continues to provide scripture through His living prophet), the words of the living prophet (or president of the church) are esteemed more valuable than ancient records. Every six months the leaders of the church formally address the church and their words in these general conferences are considered modern scripture. (see http://gc.lds.org/)
It's important to emphasize that this doesn't devalue the Bible, Book of Mormon, Doctrine and Covenants, or Pearl of Great Price. Each is singly taught as the official Sunday School curriculum for a year on a four-year rotation (actually Old Testament; New Testament; Book of Mormon; Church History, incl. Doctrine and Covenants and the Pearl of Great Price; see http://www.lds.org/manual/sunday-school?lang=eng). The words of the living prophet are just considered more timely.
The path to salvation will always be the same (the gospel of Jesus Christ), but present-day temptations like debt and drug use aren't explicitly warned about by Abraham or Noah or Moses because they weren't prevalent during their time. Because they are prevalent today, God speaks His warnings the same way He spoke His warnings in times past, through a living prophet who can and does explicitly condemn things like drug use and excessive consumer debtβmodern temptations that can make it difficult to live the teachings of Jesus Christ.
See also: http://www.lds.org/liahona/1981/06/fourteen-fundamentals-in-following-the-prophet?lang=eng