The paper describes experimental studies of hint in problem solving, as well as theoretical approaches to understanding the mechanisms underlying the hint phenomenon. The empirical results revealing the conditions of effective hinting are described with particular attention to the conditions of spontaneous transfer of auxiliary information. The conditions of hint utilization include active search for hints, resemblance between the hint source and the target task, common coding and extraction processes of the task and the hint, the temporal relation between the moments of hint and task presentation, depth of processing of the task and the hint, and reaching an impasse in the course of task solution. On the basis of the analysis of the studies following conclusions can be made. A range of experiments showed that hint use is possible only with the knowledge of its presence and intentional search of the relevant information. Probably, the instruction becomes important, when the conditions necessary for spontaneous transfer are not fulfilled. The studies on the similarity between the task and the hint and how it heightens the effectiveness of the auxiliary material showed that the use of the material that has direct answer was more often in the case of spontaneous attention. Hint may be effective independently from time of presentation, but a hint that was presented after the initial solving of the main task is more effective if it is not postponed. The deepness of the procession of the main task influenced the way the received hint was used. Also the data of the research allow stating that for the effective action of the hint, on the one side, the processed representation of the task is needed, and on the other side, the absence of fixation on repeated wrong variants of solution. Theoretical explanations of the hint effect in complex tasks are discussed, and the differences in hint use associated with individual differences in creativity are analyzed.