Field API

Rendering fields in Drupal 7

The short answer:

use field_view_field();

The long answer:

In drupal 6 it was perfectly common to poke around in the node object to get your values and print them.
With the field api and entities in drupal 7 however we need to change that habit and use the functions drupal provides us.
Luckily field_view_field() comes in here. 

$output = field_view_field('node', $node, 'field_name');

Combine it with