The following code is a step-by-step form in which the user will fill out part of a form, click on the next button, and then fill out another part of the form until the last section in which the form will be submitted. I have included some <inputs> both required and not required to show you that the user cannot proceed until the section is completed based on required input:

HTML
HTML Code:
<form>
  <fieldset>
    <legend>Contact Information</legend>
    <section>
      <label for="txtName">* Full Name</label>
      <input id="txtName" required="required" type="text" />
      <label for="txtEmail">* Email Address</label>
      <input id="txtEmail" required="required" type="email" />
      <label for="txtPhone">* Phone Number</label>
      <input id="txtPhone" required="required" type="tel" />
    </section>
  </fieldset>
  <fieldset>
    <legend>Questions, Comments, or Concerns</legend>
    <section>
      <label for="cboType">Inquery Type</label>
      <select>
        <option>Question</option>
        <option>Comment</option>
        <option>Concern</option>
      </select>
      <label for="txtDescription">Description</label>
      <textarea id="txtDescription"></textarea>
    </section>
  </fieldset>
  <footer>
    <input id="btnLeft" type="button" value="< Back" />
    <input id="btnRight" type="button" value="Next >" />
  </footer>
</form>
CSS
Code:
form fieldset {
  border-width: 0;
  margin: 0;
  padding: 0;
}

form fieldset legend {
  border-bottom: 3px dotted rgb(102, 102, 102);
  font-size: 1.5em;
  margin: 0;
  padding: 0;
  width: 100%;
}

form fieldset section label {
  display: block;
  padding-top: 1em;
}

form fieldset section input, form fieldset section select, form fieldset section textarea {
  box-sizing: border-box; /*select width fix */
  margin: 0 2%;
  padding: .5em 1%;
  width: 94%;
}

form footer {
  padding-top: 1em;
}

form footer input[type="button"] {
  background: rgb(202, 60, 60);
  border-radius: 4px;
  color: rgb(255, 255, 255);
  cursor: pointer;
  margin: 0 2%;
  padding: 1em;
  text-shadow: 0 1px 1px rgba(0, 0, 0, 0.2);
}

form footer input[type="button"]:last-child {
  background: rgb(28, 184, 65);
  float: right;
}

form footer input[type="button"]:disabled {
  background: rgb(102, 102, 102);
  color: rgb(224, 224, 224);
  cursor: not-allowed;
}
JQuery
Code:
$(function() {
  //Hide all but the first element
  $('form fieldset:not(:first)').hide();

  //Disable the back button to begin with
  $('#btnLeft').prop('disabled', true);

  $('#btnLeft').on('click', function() {
    //get the index of the previous fieldset
    var leftIndex = $('form fieldset:visible').index() - 1;
    changeFieldset(leftIndex);
  });

  $('#btnRight').on('click', function() {
    //get all invalid input
    var invalid = $('form fieldset:visible').find(':invalid');

    //get the index of the next fieldset
    var rightIndex = $('form fieldset:visible').index() + 1;

    if(invalid.length > 0) {
      //inform the user that there are invalid inputs by changing the border-color
      invalid.css('border-color', 'rgb(202, 60, 60)');
    } else if(rightIndex == $('form fieldset').length) {
      $('form').submit();
    } else {
      //Set all the border-colors back to normal
      $('form fieldset:visible').find('input').css('border-color', 'rgb(255, 255, 255)');
      changeFieldset(rightIndex);
    }
  });

  $('form').on('submit', function() {
    alert('submitted!');
  });

  function changeFieldset(index) {
    //hide the visible fieldset
    $('form fieldset:visible').hide();

    //show the fieldset at the index;
    $('form fieldset').eq(index).show();

    //disable the back button(if applicable)
    $('#btnLeft').prop('disabled', index === 0);
  }
});
Fiddle: http://codepen.io/anon/pen/ZWGwdb