This is a vague and grand question but hopefully I can explain it with as little concrete examples as possible.
We recently switched to Spring MVC for our applicatio
Well in terms of your UI, Apache Tiles and Sitemesh are things you might want to look at here.
http://tiles.apache.org
http://wiki.sitemesh.org/wiki/display/sitemesh/Home
In terms of the controller layer, Spring has the @ControllerAdvice annotation which can be used to place model attributes in scope for all controllers. If, for example, you placed the navigation model in your @ControllerAdvice, no other controller would have to worry about setting it as a model attribute.
http://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html
@ModelAttribute methods can also be defined in an @ControllerAdvice-annotated class and such methods apply to all controllers. The @ControllerAdvice annotation is a component annotation allowing implementation classes to be autodetected through classpath scanning.