How do I go to Checkout Page without product in cart? I am using Commerce Donate and configured it to show donation form on checkout page. That is what actually I need. Donation form, contact info and payment form on same page.

But we cannot go to the checkout page without having some product in cart.

How can I do that?
You can add the following code to a custom module:

/**
 * Implements hook_menu_alter().
 */
function YOURMODULE_menu_alter(&amp;$items) {
  // Alter the default checkout callback to allow checkout without products.
  $items['checkout']['page callback'] = 'YOURMODULE_checkout_router';
}

/**
 * Implements hook_commerce_checkout_order_can_checkout().
 */
function YOURMODULE_commerce_checkout_order_can_checkout($order) {
  return TRUE;
}

/**
 * Displays the checkout form and create the user a cart if none exist.
 */
function YOURMODULE_checkout_router() {
  global $user;
  // Load the shopping cart order.
  if (!($order = commerce_cart_order_load($user-&gt;uid))) {
    $order = commerce_cart_order_new();
  }
  drupal_goto('checkout/' . $order-&gt;order_id);
}