Wireless Sensor Networks (WSNs) are increasingly used for monitoring applications in order to sense critical events in the environment. When a WSN is deployed (or when it restarts due to a software update), each node of the network has to perform an association procedure before being allowed to transmit data. Thus, it is crucial to reduce the time required to have a fully-operational network, which is the time required for all the nodes to be associated. In this chapter, we describe a mechanism that enables nodes to initiate their association procedure at the right time, rather than when they are deployed. The mechanism is distributed and does not make any assumption on the underlying topology. We evaluate our mechanism on several random network deployments, as a function of the duty cycle and of the number of nodes. Extensive simulations show that our mechanism is able to improve the association phase by significantly reducing its duration, and by increasing the number of nodes that can be associated in a given duration.