Ad hoc networks are formed by mobile or stationary devices communicating over wireless links without using a fixed networked infrastructure. They may support applications in the area of military operations, disaster recovery, and spontaneous collaboration among users in a meeting, or during a lecture. Due to limited transmission range, communication between any two devices requires collaborating intermediate forwarding network nodes. Communication may be trivially based on simply flooding the entire network. However, more elaborate routing algorithms are essential for the applicability of ad hoc networks, since energy and scarce bandwidth have to be conserved in low-powered wireless devices. This tutorial is focused on memoryless single-path geographic routing algorithms that perform well even in large ad hoc networks. The next section outlines single-path greedy routing strategies and recent improvements to those algorithms. his article provides a tutorial for this class of geographic routing algorithms, and discusses recent improvements to both greedy forwarding and routing in planar graphs.