Tandem queues are often used for performance modeling in production lines, computer systems and communication networks. Consider a series of tandem first-come-first-served queues with single servers. The buffers may be finite or infinite. When a finite buffer is full, the upstream server may suffer from transfer blocking or service blocking. A job's service requirements at various servers may be correlated. A transient analysis shows that, if the network is open, then response time decreases if a server is speeded up, or a finite buffer increases in size, or service blocking is changed to transfer blocking at some server; if the network is closed, then such changes increase the throughput. The analytic technique is elementary, and the equations can be used to simulate a network.