Drupal core fields:

<?php print $fields['title']->content; ?>
<?php print $fields['body']->content; ?>
<?php print $fields['nid']->content; ?>

Print the teaser:

<?php print $fields['teaser']->content; ?>

CCK fields:

<?php if ($fields['field_location_value']): ?>
<?php print $fields['field_image_fid']->content; ?>

If a field is optional, you might want to say "if field is not empty", like this:

<?php if (!empty($fields['field_image_fid']->content)) {
  print $fields['field_image_fid']->content; }
?>

Especially if you want to add a div or h2 around the print, like this:

  <?php if ($fields['field_location_value']): ?>
    <div class="sample"><?php print $fields['field_location_value']->content; ?></div>
  <?php endif; ?>
  <?php if ($fields['field_venue_value']): ?>
    <<div class="sample">><?php print $fields['field_venue_value']->content; ?></div>
  <?php endif; ?>

Finally, here's a great tutorial on views row theming from the good folks at Mustardseed Media [source]