Sticky Footer is very specify and has a lot tricks. But, only two tricks is correct and work in different situation.
First, you must think and choose which trick you will use:

• if footer doesn't be responsive - use CSS trick;
• if footer doesn't change height - use CSS trick;
• if footer will be responsive - use jQuery trick;
• if footer will be change height - use jQuery trick.

You ask me:
Why we choose trick and what difference between CSS trick and jQuery trick ?

Yes, we may always use jQuery trick. It's better and more fail-safe.
But, I always keep the rule: " If you can implement by CSS and it not broke your project do it ". CSS much better for browser speed, doesn't have to be evaluated by the browser. jQuery has to be evaluated by the browser. But, you always must look ahead what will be with your stuff.

If you choose what trick use, you can start to create or edit html file.
HTML structure must be:

<div id="wrapper">

  <div class="header">...</div>
  
  <div class="container">...</div>
  
  <div id="push"></div>
  
</div>

<div id="footer">
  ...
</div>

The footer needs to sit outside the wrapper because we will be checking the height in wrapper.
id="push" need it because we prepared space for footer when container will be more.
Let's start:

###CSS trick

/* General */
* {
    margin: 0;
    padding: 0;
}
html,body {
    height: 100%;
}

/* Main */
#wrapper {
    min-height: 100%;
}
#push {
    height: 55px;
}
#footer {
    height: 55px;
    margin-top: -55px;
}

###jQuery trick If we want to use jQuery we include library jQuery Donwload jQuery and file main.js.

<script src="http://code.jquery.com/jquery-2.1.0.min.js"></script>
<script type="text/javascript" src="main.js"></script>

Our html file look little bit different like file for CSS trick:

<div id="wrapper">

    <div class="header">...</div>
    
    <div class="container">...</div>
    
</div>

<div id="js-footer" class="footer">
    ...
</div>

Adding css style for our blocks:

#wrapper {
    position: relative;
}
.footer {
    width: 100%;
    padding: 10px 0;
}
.footer-sticky {
    position: absolute;
    bottom: 0;
}
.footer-static {
    position: static;
}

And last step is write jQuery code for footer:

$(function() {
    //Variables
    var footer = $('#js-footer'),
        footerHeight = footer.innerHeight();

    //Now we check document height and window height
    if (($(document.body).height() + footerHeight) < $(window).height()) {
        footer.addClass('footer-sticky'); //If window height more than document height we add class
    } else {
        footer.addClass('footer-static'); //If window height less than document height we add class
    }
});

If you have some questions, problems or improvement for this tricks create issue and we will discuss.
Thank you!

MIT License