何时/如何在使用指针后正确删除指针?

只是学习指针并正在解决这个问题，我很困惑。只要我在使用指针后删除它们，那么我应该可以使用它们，这显然不是这样，因为它不起作用。我使用new，它在堆上分配内存，但它从堆栈中获取地址，是那里的问题，一些澄清和最佳实践建议将不胜感激。

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
// initialize variables
double hours=0.0,rate=0.0,overtime=0.0,pay = 0.0;
double *dptr1 = new double;
double *dptr2 = new double;
double *dptr3 = new double;
// getting input from user
cout << "Enter standard hours worked: ";
cin >> hours;
cout << "Enter rate of pay: ";
cin >> rate;
cout << "Enter overtime hours(enter 0 for no overtime): ";
cin >> overtime;
dptr1 = &hours;
dptr2 = &rate;
dptr3 = &overtime;

// calculate pay
pay = hours * rate + (1.5 * rate * overtime);
// print out the results
cout << setw(4) << "Standard Hours " << setw(8) << "Rate " << setw(12) << "Overtime " << setw(16) << "Pay " << endl;
cout.setf(ios::floatfield,ios::fixed);
cout <<setprecision(0)<< setw(8) << *dptr1 <<setprecision(2)<< setw(13)<< *dptr2 <<setprecision(0)<< setw(13)<< *dptr3 << setw(18)<<setprecision(2)<<pay;
delete dptr1;
delete dptr2;
delete dptr3;

}