Recent progress of wireless technologies has initiated a new trend in learning environments, called ubiquitous learning (u-learning), which is able to sense the situation of the learners, and hence provide more adaptive supports. Many researchers have investigated the development of such learning environments; nevertheless, the criteria of establishing a u-learning environment have not been clearly defined, not to mention the strategies for conducting effective learning activities. To cope with these problems, we shall present in this paper the basic criteria of constructing a u-learning environment, such that subsequent researchers can identify and check the necessary items while establishing the learning environment. Moreover, several strategies for conducting u-learning activities are proposed, based on the given criteria.