Our legacy code often comes along with a large number of interfaces and dependency injection and it's difficult to find where the code actually 'does something'. So the only way I can understand what the code is doing is by stepping through it in a debugger.
If I just try to read it, I end up half a dozen classes away from the method I'm trying to understand in no time.
If methods are factored and named well, the name tells you what it does and you shouldn't have to look at the implementation unless its not doing what it says.
I've found that good OO programs are understood by understanding the classes and messages between them, not by reading the implementations of those methods. Look for the big picture, not the details.
As it looks like you're using .Net, you might want to look into resharper as it implements a 'go to implementation' as well as a 'go to declaration':
http://www.jetbrains.com/resharper/webhelp/Navigation_and_Se...