A snippet for social sharing buttons in a Shopify theme. Notice the use of theme settings to show/hide each button.

supply-social-sharing

{% comment %}

  This snippet is used to showcase each collection during the loop,
  'for product in collection.products' in list-collections.liquid.

{% endcomment %}
{% assign shareCountClass = '' %}

{% if template contains 'article' or template contains 'blog' %}
  {% capture permalinkURL %}{{ shop.url }}{{ article.url }}{% endcapture %}

  {% unless settings.social_sharing_count %}
    {% assign shareCountClass = 'no-count' %}
  {% endunless %}

{% elsif template contains 'product' %}
  {% capture permalinkURL %}{{ shop.url }}{{ product.url }}{% endcapture %}

  {% unless settings.social_sharing_count %}
    {% assign shareCountClass = 'no-count' %}
  {% endunless %}

{% endif %}

<div class="social-sharing {{ shareCountClass }}" data-permalink="{{ permalinkURL }}">

  {% if settings.share_facebook %}
    <a target="_blank" href="//www.facebook.com/sharer.php?u={{ permalinkURL }}" class="share-facebook">
      <span class="icon icon-facebook"></span>
      <span class="share-title">Share</span>
      <span class="share-count">0</span>
    </a>
  {% endif %}

  {% if settings.share_twitter %}
    <a target="_blank" href="//twitter.com/share?url={{ permalinkURL }}" class="share-twitter">
      <span class="icon icon-twitter"></span>
      <span class="share-title">Tweet</span>
      <span class="share-count">0</span>
    </a>
  {% endif %}

  {% if template contains 'product' %}

    {% if settings.share_pinterest %}
      <a target="_blank" href="//pinterest.com/pin/create/button/?url={{ permalinkURL }}&amp;media={{ product.featured_image | product_img_url: 'original' }}&amp;description={{ product.title | escape }}" class="share-pinterest">
        <span class="icon icon-pinterest"></span>
        <span class="share-title">Pin it</span>
        <span class="share-count">0</span>
      </a>
    {% endif %}

    {% if settings.share_fancy %}
      <a target="_blank" href="http://www.thefancy.com/fancyit?ItemURL={{ permalinkURL }}&amp;Title={{ product.title }}&amp;Category=Other&amp;ImageURL={{ product.featured_image | product_img_url: 'original' }}" class="share-fancy">
        <span class="icon icon-fancy"></span>
        <span class="share-title">Fancy</span>
      </a>
    {% endif %}

  {% endif %}

  {% if settings.share_google %}
    <a target="_blank" href="//plus.google.com/share?url={{ permalinkURL }}" class="share-google">
      <!-- Cannot get Google+ share count with JS yet -->
      <span class="icon icon-google"></span>
      <span class="share-count">+1</span>
    </a>
  {% endif %}

</div>

How to share product in instagram, please share code