[dmlorenzetti]

The main thing I do is try to implement very thorough unit tests. I find that the act of writing the tests helps me think through the interface to the code, which in turn helps me isolate the caller from implementation details. It also helps make sure an individual module doesn't try to do too much or too little-- the unit test will start to feel "baggy" in the first case, and will look pretty thin in the other.

If you haven't read "Working Effectively with Legacy Code" by Michael Feathers, I would strongly recommend it. The book officially is about how you get existing code under test, but its techniques orient around moving the code to a better organization.

The book "Large Scale C++ Software Design" by Lakos lists some actual, computable, metrics for assessing how interconnected your code is (and hence how hard to change). Never having used those metrics, I can't recommend them one way or the other; I just know they exist.

[xackpot]

Thanks for the suggestions. I checked out the book by Michael Feathers and it definitely looks helpful. I have embarrassingly low number of unit tests which I need to take care of and introduce more rigorous testing into our code.