Adaptive plans aim to anticipate uncertain future changes by combining low-regret short-term actions with long-term options to adapt, if necessary. Monitoring and timely detection of relevant changes, and critical transitions or tipping points is crucial to ensure successful and timely implementation and reassessment of the plan. Although efforts have been made to identify signposts to monitor, the question remains how to design a signal monitoring system that detects and anticipates (future) change to support adaptive planning. For example, to support water related infrastructure investments under uncertain climate change. What are good signposts to monitor and how to wisely analyse them to get timely and reliable signals for adaptation? In this paper, we present a framework for designing and using a monitoring plan as part of the Dynamic Adaptive Policy Pathways (DAPP) approach for decision making under uncertainty. We use the following criteria to evaluate signposts and their critical signal values: measurability, timeliness, reliability, convincibility and institutional connectivity. We illustrate the approach based on the signal monitoring system for the adaptive plan developed by the Delta Programme in the Netherlands.