A single block of code enclosed in { } should not span more than a couple of pages. Split up any bigger blocks into several smaller, simpler procedures.
When your code starts to run into the right margin, it's time to split the procedure into several smaller, simpler procedures.
Always define a constructor, destructor, and copy constructor for a class. If using the C++ defaults, "define" these routines with a comment such as:
class example { public: // Example -- default constructor