During designs and implementations, your goal as a software architect should be to minimize the amount of coupling that exists between modules. Modules should be designed to be as independent as possible.
Coupling can be reduced by eliminating or reducing the number of unnecessary dependencies. For any coupling that must exist, it should be the lowest type that is necessary. Loose coupling reduces complexity and increases maintainability and reusability.
Coupling typically affects the level of cohesion, so that loose coupling correlates with high cohesion and tight coupling correlates with low cohesion.