#include <iostream>
using namespace std;

// Pre-declare class template...
template <class T> class MyTemplate;

// So we can pre-declare inserter...
template <class T> ostream &operator<<(ostream &stream, const MyTemplate<T> &t);

// So when we define the class template...
template <class T> class MyTemplate {
    // We can declare inserter a friend.
    friend ostream &operator<< <T> (ostream &stream, const MyTemplate<T> &t);
    ...
}

// Now inserter can access MyTemplate's private members
template <class T> ostream &operator<<(ostream &stream, const MyTemplate<T> &t) {
    ...
}