Management of Mobile Ad-hoc NETworks (MANETs) is very difficult, because the movement of nodes is unpredictable, frequently changing the topology of the network. Consequently, Service Discovery (SD) in the network, a perquisite for efficient usage of network resources, is a complex problem. There are many issues in SD for MANETs. This paper aims to classify and compare existing SD protocols for MANETs by grouping them based on their SD strategies and service information accumulation strategies, and propose an efficient approach for addressing the inherent issues.