This is (a rubbish one) just to help me remember the DD tags:
<context-param>
<param-name>n</param-name>
<param-value>v</param-value>
</context-param>
Whereas Servlet params are “in-it”:
<servlet>
<init-param>
<param-name>n</param-name>
<param-value>v</param-value>
</init-param>
…
</servlet