Continuously integrate new code
As soon as new code is finished it should be integrated into the code base. By that it is not only ensured that all members of the development team get access to new code, it also minimises the risk of running into incompatibilities and reduces the complexity of merging changes.
In a recurring fashion this could happen at the end of development day. Also partly finished features can already be pushed into the base as long as they meet the project's quality minimums (etc. testable/tested, documented). At the beginning of the next development day changes would get individually pulled into the working copy.
Maximise coverage of automated tests
Testing code is a crucial part in reaching a certain level of quality and stability. To minimise the workload needed the process should be automated where possible. This can be done with unit tests using state of the art testing frameworks (JUnit, Selenium, etc) to further reduce workload.
It should be also possible to combine testing with continuous integration. This gives the advantage of running tests as often as possible and getting the chance to react to issues quickly.
Think ahead and stay flexible
Each team member should keep the future constantly in mind. As the application grows requirements might (or most likely "will") change. To be able to react and implement these changes it is important to always develop for scalability and flexibility. This accounts not only for the development members but also for the management members of team. The management should always evaluate new features with what might come next.
Keep it simple
Always create the simplest solution for a problem that will work and deliver for the minimum requirement. Maintaining a simple, clean and open design ensures that the application can be easily extended while staying focused and meeting dead lines.