This css tip adds a great looking box shadow to your web components. I always apply this styling to all of my bootstrap cards.
All you have to do is add this to your css file:
box-shadow: 0px 2px 4px rgba(0, 0, 0, 0.18);
I got this idea from Steve Schoger's tweet. This tweet is part a series of tweets that offer some pretty amazing design advice. You should check them out.