Software projects are among the failure prone projects in engineering and software requirements problems have been attributed to be one of main reasons to software project failures. There are many techniques and methodology developed for practitioners to use in working with software requirements, which makes it impossible for one to master them during formal education. In addition, many of the practitioners are coming from different disciplines. Thus they are required to learn in practice. Previous studies have shown informal learning (i.e. not planned or run by institutions or organizations) to be more effective and more used in workplace learning situations. The study investigates how the requirements engineering skills are and can be learned in workplace especially informally. By comparing the results obtained by the literature study and empirical study the recommendations are given on how one can recognise, utilise, and encourage the informal learning activities to develop requirements engineering skills. The study does not rule out the need to have the formal education and training in requirements engineering but identify it as an important prerequisite and/or complement. It provides insight on how informal learning practices are utilised by practitioners who are rather experienced in requirements engineering and how they could try to recognise and/or utilise other learning opportunities presented by previous literature. It furthermore offers general recommendations of how to utilise the informal learning for developing requirements engineering skills and other related disciplines.