It is known that the resources that limit the overall performance of the system are the congested ones, referred to as bottlenecks. From the knowledge of the bottleneck stations with a limited computational effort it is possible to derive asymptotic values of several performance indices. While identifying the bottleneck stations under a single-class workload is a well-established practice, no simple methodology for multiclass models exists. In this paper we present new algorithms for identifying the bottlenecks in multiclass queueing networks with constant-rate servers. We show how the application of assessed techniques, such as the ones related to the convex polytopes, can provide insights on the performance of a queueing network. The application of our techniques to the asymptotic analysis of closed product-form networks is also investigated.