How to add custom node field into page title?
A hook_preprocess_page function in your template.php file would certainly be one way to do it:

function MYTHEME_preprocess_page(&amp;$vars) {
  $node = menu_get_object();
  if (isset($node-&gt;nid) &amp;&amp; $node-&gt;type == 'article') {
    $data = $node-&gt;field_custom_field[$node-&gt;language][0]['value'];

    $vars['title'] = $vars['title'] . ' ' . $data;
  }
}


In page.tpl.php your $title variable should contain your new string based on the field.

You'll probably want to do a couple of extra checks in there as well, for example making sure the node is of the right type, etc.

EDIT

To address your comments I guess you'd want to do something like this:

$area_size = $node-&gt;field_area_size[$node-&gt;language][0]['value'];
$location = $node-&gt;field_location[$node-&gt;language][0]['value'];

$vars['title'] = "$vars[title] $area_size sq ft ($location)";