Wolves communicate through many forms of vocalization, including their growl, whimper, whine, bark, squeal, and howl.  Each vocalization carries different meaning. 
Whimpering or whining is often a display of friendliness. 
Wolves use growls to enforce pack hierarchy or to threaten; while their barks are used to signal alarm. 
One of the most haunting, and often beautiful, forms of communication is the wolf pack howl.  Howls are used by the pack to bring a pack together, for celebration or to protect their territory.  Each wolf has an individual sound and each produces their own unique note.
In humans, the howl either provokes pleasure or fear.  A human can generally determine when only one wolf is howling, yet when two or more wolves are howling it is often difficult to determine how many wolves are taking part in the wolf chorus.  Even though wolves, generally, fear humans they will readily respond to human howls.  So if you ever have the opportunity to be near a wolf or a wolf pack feel free to enter in communication with them.

Besides vocalization wolves communicate through body language.  Wolves use their whole body in communication; their stance, their facial expressions, their stares, even their tails. 
One show of dominance is when a wolf stands on its hind legs, while a submissive wolf rolls over on their back, exposing their underside. 
The tail is one of the most telling forms of body language utilized by the wolf. The position of the tail can indicate dominance, aggression, submission, fear, as well as other communications.  When the tail is high and curled it shows dominance.  A high wagging tail often reflects the wolf is in a playful mood.  The tucked tail is a show of submissiveness to a dominant wolf, or the sign of fear.  When a wolf senses danger or is about to be attacked their tail will be pointing straight out, this may also indicate the wolf is aroused.  When the wolf is relaxed he will often have his tail hanging straight down.

A subordinate wolf will cringe towards the leader with tail low and bent legs, ears back and down, in a submissive nature. At other times, active submission involves a group of subordinate wolves surrounding the dominant wolf with their noses up against it. Sometimes the pack will howl.

Various facial muscles, eyes, ears and the nose are extremely important when wolves are expressing their feelings. Bared teeth, an open mouth, ears erect and pointed forward indicate a threat by a dominant wolf.

Wolves communicate and mark their territories by scent. They often do this by urinating near the edges of their territory, and on stumps, rocks and logs that are within their territory. Most of this is done by the dominant wolves, usually the alpha male.
Wolf Communication