How can I improve the accessibility of my web forms?

<!-- BEGIN COPY / PASTE -->
    <form>
      <div>
        <label for="name">Name:</label>
        <input type="text" id="name" name="name" aria-required="true">
      </div>
      <div>
        <label for="email">Email:</label>
        <input type="email" id="email" name="email" aria-required="true">
      </div>
      <div>
        <label for="message">Message:</label>
        <textarea id="message" name="message"></textarea>
      </div>
      <button type="submit">Submit</button>
    </form>
    <!-- END COPY / PASTE -->