neilgee

This plugin adds support for placeholder text in browsers that don’t support this HTML5 feature including Internet Explorer 6.
The plugin just activates the placeholders.js script by James Allardice http://jamesallardice.github.io/Placeholders.js/
There is no further configuration required.
For HTML input elements use the placeholder attribute and add a value, this value is removed when a user inputs the field. http://coolestguidesontheplanet.com/add-a-label-into-a-text-input-field-in-a-html-form/#html5
The script is 4KB and is set to load in the footer and has no library dependencies.
<h3>Usage</h3>
Just activate the plugin which loads the script, their is no further configuration.

Placeholder Text

This plugin adds support for placeholder text in browsers that don't support this HTML5 feature.

AMP-MODE

Scott DeLuzio

If you sell a product through your WooCommerce store that requires you to collect some additional information from your customers before they complete their purchase, this plugin is exactly what you need.
Pro Version Now Available 
<a href="https://conditionalcheckoutfields.com/downloads/conditional-woo-checkout-field-pro/" rel="nofollow ugc">Update to Pro</a> to get even more features.
<ul>
<li>Display an unlimited number of custom conditional fields at checkout (free version only allows one).</li>
<li>Display each conditional field on an unlimited number of products, product variations, or categories of products (free version only allows the field to display for one product).</li>
<li>Increased variety of available input fields including: Text box, multi-line text area, drop-down/select menu, country list, state list, check boxes, password, radio buttons, and date picker.</li>
<li>Bonus: Easily edit any of the default WooCommerce checkout fields without having to edit any code.</li>
</ul>
Get the pro version by <a href="https://conditionalcheckoutfields.com/downloads/conditional-woo-checkout-field-pro/" rel="nofollow ugc">clicking here</a>.
This plugin lets you configure an additional field to be displayed at checkout for your customer to fill out provided a certain product is in the customer’s cart.
The plugin allows you to customize this additional field’s
<ul>
<li>Title</li>
<li>Input type (text box, text area, or select/drop down menu)</li>
<li>Label</li>
<li>Placeholder text</li>
<li>CSS Class</li>
<li>Whether or not the field is required (and the error message to display if it is required but not filled out)</li>
<li>Whether or not to add the customer’s input to the order email or invoice</li>
</ul>
This plugin requires your site to have WooCommerce installed in order to work. It is not compatible with other e-commerce plugins.

Conditional WooCommerce Checkout Field

Display a custom field at checkout in your WooCommerce store if a certain product is in the customer's cart.

Placeholder Text vs Conditional WooCommerce Checkout Field