Answer 1

there is no "true" structure, but i like this way
main.cpp
//SYS includes
#include<iostream>

// User includes
#include "myclass.h"

// Globals

// function prototypes or structs or enums

//main
main(){
// Declare variables
int day;

// Declare objects
myObject o;

// Memory deallocation
delete ptr;

// SYS EXIT SUCCESS
return 0;
}

myclass.h
// SYS includes <- keep these in the .cpp as much as possible
//User includes

// structs or enums

class myclass {
public:
private:
protected:
}