It was thought for a long time that it was the alpha male that ruled the packs, but it has now been proven that the alpha female can control the pack, while the alpha male could just be the highest ranking male there. I know of at least one pack that is ruled by the alpha female. Below the alpha male and female, the pack all knows its place in the hierarchical structure of the pack. Most disagreements rarely end in serious fights. If, however, either the alpha male or female dies, or gets killed, there can be in-fighting within the pack to gain the position.
Wolves have a very varied and complex communication system.
To us, who are used to a more vocal language, it is hard to understand the extent of this. Wolves communicate through postures, looks, glances, a growl, howling, whimpers, whines, and barking. Most of the time a subtle movement of the body, or a glance is all that is needed to get across what is needed, especially when asserting dominance over another. Showing direct eye contact, which is seen to be aggressive, could show this. You can usually tell which members of the pack are the highest ranking in the hierarchy by how erect the tail is in the air.