Field theming functions
print render(field_view_field('user', $user, 'field_avatar', array('settings' => array('image_style' => 'post_avatar'))));
Results in user object (from user_load) + field name and settings array.
You can also remove the label.
field_view_value is the same but with one element.
Example: displaying the first image in a field with multiple images:
$image = field_get_items('node', $node, 'field_image');
$output = field_view_value('node', $node, 'field_image', $image);
field_get_items is handy too. You don't have to look it up in the entire node object anymore, like:
But with field get items you don't have to woory about languages etc.
Example: hide label when field empty:
check with field_get_items if return is FALSE.