Using Bootstrap's Offset Classes
Bootstrap 3 provides offset classes (col-md-offset-*) to push columns to the right, effectively centering them.
Example:
<div class="container">
<div class="row">
<div class="col-md-6 col-md-offset-3">
<!-- Your content here -->
<p>This div is centered within a 12-column container.</p>
</div>
</div>
</div>