How to change the HTML of the commerce shipping service form on checkout pages? Right now, the HTML of the commerce shipping service consists  by input buttons, where you select the desired method.
I'd like to is to have it in the form of a select, and - more importantly - have no default shipping method selcted.
How to do it?
As suggested by clive, You should try this:

function MYMODULE_form_commerce_checkout_form_alter($form, &amp;$form_state, $form_id) {
  ...
}


or

function MYMODULE_form_alter($form, &amp;$form_state, $form_id) {
  switch ($form_id) {
    case 'commerce_checkout_form':
      ...
    break;
}