Dynamic Random Access Memory (DRAM) has been prevalent over the past few decades as main memory component. The demand of higher memory capacity is increasing continuously, while scaling of DRAM is reaching its boundaries. As we scale DRAM to smaller feature size, difficulties in fabrication, leakage power, and energy consumption become significant. Therefore, memory technologies, which have better scalability feature, will be the future of memory systems. To overcome these limitations, search for a new memory technology is necessary and Phase Change Memory (PCM) is the most promising. PCM is non-volatile memory with better scalability and less leakage power than DRAM. It is a resistance-based memory, which doesn't need to be refreshed. PCM suffers more write latency and less write endurance. The write latency of PCM is higher than its read latency by almost 8 times. A large number of researches have been done on reducing write latency of PCM. This research will focus on studying different approaches and techniques in order to reduce write latency on various aspects. Then, techniques employed to reduce write latency of PCM such as PreSET, Partial-SET, Flip-N-Write, two-stage-write, and two-stage-write-inv are introduced. Conclusively, a performance comparison of each technique is discussed.