Needs for Structural Health Monitoring in the last decades were rapidly increasing. Research, development and implementation activities related to SHM were of such an importance, that SHM became a distinct branch of engineering. Several recommendations for codes, vocabulary and university courses are proposed and / or in route of development. The amount of published material is increasingly growing. SMARTEC SA is involved in SHM for more then a decade, having more than 350 realized projects worldwide. Experience gathered from these projects was precious not only from the point of view of development and implementation of monitoring components, but also for exploring SHM needs and benefits, and for understanding SHM process complexity. In this paper, lessons learned in more than 350 SHM projects are presented. Basic notions related to structural health monitoring are introduced. Structural health monitoring aims, needs and benefits are discussed. The importance of whole lifespan monitoring is highlighted. Core activities of monitoring process such as monitoring strategy, installation and maintenance of monitoring equipment and data management are presented and discussed. The monitoring actors are identified and their interaction with monitoring process is analyzed.