How can I set up free shipping?
I use Flat Rate module to do the same. You can set free shipping with help of this module very easily.

Once you enable the module, navigate to Store-&gt;Configuration-&gt;Shipping-&gt;Shipping Method-&gt;Flat Rate.

You will find Flat Rate under Shipping Method tab. Click Add a flat rate service.

Add something kind of Free Shipping, give it Title, Display title &amp; Base Rate as 0.

Now visit Shipping Service tab. You will find your added flat rate service in there. Click Configure Component &amp; put any condition you like e.g. Data Comparison to commerce-order:commerce-order-total:amount for any amount. 

Now When ever your condition matches, this Free shipping service will apply if you have put Shipping service in Shipping pane under Store->Configuration>Checkout settings.