{% set limitCriteria = craft.entries.limit(4) %}
{% set similarEntriesByTags = craft.similar.find({ element: entry, context: entry.contentTag, criteria: limitCriteria }) %}
<h2>関連エントリ</h2>
<ul>
{% for similarEntry in similarEntriesByTags %}
    <li><a href="{{ similarEntry.url }}">{{ similarEntry.title }}</a></li>
{% endfor %}
</ul>