Wireless sensor networks is one of the active research area now a days due to its vast applications in different fields such as defense, civilian and medical fields. One of the basic challenges in the design of Wireless Sensor Network (WSN) is maximizing their lifetime because of the sensors placement in remote places which is having batteries as power sources. To extend the WSN lifetime, energy management is the most important and critical aspect, for that we need different techniques in different aspects of WSN. This paper presents some methods which will be useful to minimize energy consumption in sensor networks and to increase lifetime of the WSN. Sensor nodes are using batteries as their power sources, effective and efficient utilization of these power sources is essential in order to use sensor networks for longer period hence it is required to reduce data transfer rate inside sensor networks, reduce amount of data that required to send to base station. For this, data aggregation methods are useful for aggregating data in an effective energy efficient manner so that network lifetime will enhance. In most applications once WSN deployed, it should continue to work for a long period of time, without the maintenance of the nodes and the replacement of their energy sources. Each sensor node in the network consumes power in different stages like sensing data, processing data and transmitting/receiving. In all stages minimizing energy consumption is required. Therefore routing protocols designed which should minimize power consumption in every stage of WSN because of its effective function. © 2005 - 2014 JATIT & LLS. All rights reserved.