Combining fields in preprocess template
Once you have preprocessed your variables in theme_preprocess_node() you can print them in node.tpl.php

The best practices would imply to declare one node.tpl.php per content type like this : node--my-content-type.tpl.php replacing my-content-type by the name of your own content.

In theme_preprocess_node() the best way to get the value of a field would be like this :
In template.php the first function is only here so you can have one preprocess function per content type.

/**
 * Override or insert variables into the node templates.
 *
 * @param $vars
 *   An array of variables to pass to the theme template.
 * @param $hook
 *   The name of the template being rendered ("node" in this case.)
 */
function mytheme_preprocess_node(&amp;$vars, $hook) {
  // Optionally, run node-type-specific preprocess functions, like
  // mytheme_preprocess_node_page() or mytheme_preprocess_node_story().
  $function = __FUNCTION__ . '_' . $vars['node']-&gt;type;
  if (function_exists($function)) {
    $function($vars, $hook);
  }
}


Then you can declare your function for your content type and get the value of your fields with field_get_items() and field_view_value() in order to only get the value and not all the divs all around the field value.

/**
 * Override or insert variables into the node templates.
 *
 * @param $vars
 *   An array of variables to pass to the theme template.
 * @param $hook
 *   The name of the template being rendered ("node" in this case.)
 */
function mytheme_preprocess_node_my_content_type(&amp;$vars, $hook) {
  $node = &amp;$vars['node'];
  $first_name = field_get_items('node', $node, 'field_first_name');
  $last_name = field_get_items('node', $node, 'field_last_name');
  $vars['first_name'] = field_view_value('node', $node, 'field_first_name', $first_name[0]);
  $vars['first_name'] = field_view_value('node', $node, 'field_last_name', $last_name[0]);
}


and then in your node--my-content-type.tpl.php you can print your variable like this :

&lt;?php print render($first_name); ?&gt; &lt;?php print render($last_name); ?&gt;