As web-based information systems usually run in concurrent environment, the complexity for implementing and testing those systems is significantly high. Therefore it is useful to have guidelines to introduce concurrency control, avoiding ad hoc control strategies, which may have a negative impact in efficiency and may not guarantee system safety. This paper defines guidelines for concurrency control in web-based information systems implemented in Java with relational databases. In particular, we show where Java and relational database concurrency control mechanisms should be used in order to implement our concurrency control strategy. Additionally, we analyze the performance of different concurrency controls approaches. The main point of the guidelines is to guarantee system correctness without redundant concurrency control, both increasing performance and guaranteeing safety.