Minimal MailChimp custom form (for a WordPress template)

mc_signup.php

<!-- Begin MailChimp Signup Form -->
<div id="mc_embed_signup">
	<form action="[grab the URL from the MC form builder]" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" class="validate">
		<div id="field-firstname" class="field">
			<label for="mce-FNAME" class="assistive-text"><?php _e( 'First name' ); ?></label>
			<input type="text" value="" name="FNAME" class="input" id="mce-FNAME" placeholder="<?php _e( 'First name' ); ?>">
		</div>
		<div id="field-lastname" class="field">
			<label for="mce-LNAME" class="assistive-text"><?php _e( 'Last name' ); ?></label>
			<input type="text" value="" name="LNAME" class="input" id="mce-LNAME" placeholder="<?php _e( 'Last name' ); ?>">
		</div>
		<div id="field-email" class="field">
			<label for="mce-EMAIL" class="assistive-text"><?php _e( 'Email address' ); ?></label>
			<input type="email" value="" name="EMAIL" class="input" id="mce-EMAIL" placeholder="<?php _e( 'Enter your email address' ); ?>" required="required">
		</div>
		<div class="submit">
			<input type="submit" value="<?php _e( 'Sign up' ); ?>" name="subscribe" id="mc-embedded-subscribe" class="button">
		</div>
	</form>
</div>
<!--End mc_embed_signup-->