In the nowadays heterogeneouswireless environment, a plethora of access networks have to be inter-connected in an optimal manner to meet the always best connected paradigm. This paper highlights some of the main technical challenges in heterogeneouswirelessnetworks underlying seamless verticalhandover making as a fundamental feature to all future networking endeavors. It provides a survey on the verticalmobilitymanagement process and mainly focuses on decision making mechanisms. After presenting the related standards, the main verticalhandover approaches in the literature are analyzed and compared. The paper also points out the importance of multihoming in a such heterogeneous environment and provides an overview of the most known supporting mobility protocols. Finally, the main research trends and challenges are discussed.