<!-- By reference -->
<label for="first_name">First Name</label>
<input type="text" id="first_name" name="first_name">
<!-- By wrapping -->
<label>First Name
<input type="text" name="first_name">
</label><label for="id_of_what_you're_labeling"></label>
<!-- for example-->
<label for="username"></label>
<input type="text" id="username"><!-- Implicit -->
<label>First Name
<input type="text" name="first_name" />
</label>
<!-- Explicit -->
<label for="firstName">First Name</label>
<input type="text" id="firstName" name="first_name">
<!--
Note: the 'for' attribute is mapped to the 'id' and NOT name or type
So if id='BobSponge', then for='BobSponge'
-->