Placeholder text in form fields

Do you want to set label as placeholder? I am afraid there is not easy way to do it. You need to edit file
amember/application/default/views/_form.phtml
and replace code

PHP:

$renderer = new Am_Form_Renderer_User();

with

PHP:

class Am_Form_Renderer_Custom extends Am_Form_Renderer_User
{
    public function renderElement(HTML_QuickForm2_Node $element)
    {
        list($_) = $element->getLabel();
        if ($_) {
            $element->setAttribute('placeholder', $_);
        }
        return parent::renderElement($element);
    }
}
$renderer = new Am_Form_Renderer_Custom;

I suggest to copy this template to your custom theme folder so next upgrade do not override your changes.
http://www.amember.com/docs/Themes_and_Templates

These fields just has not labels so you do not see placeholders.
You can use the following workaround:

PHP:

class Am_Form_Renderer_Custom extends Am_Form_Renderer_User
{
    public function renderElement(HTML_QuickForm2_Node $element)
    {
        list($_) = $element->getLabel();
        if ($element->getName() == 'name_f') {
            $_ = 'First Name';
        }
        if ($element->getName() == 'name_l') {
            $_ = 'Last Name';
        }
        if ($_) {
            $element->setAttribute('placeholder', $_);
        }
        return parent::renderElement($element);
    }
}
$renderer = new Am_Form_Renderer_Custom;