Word of mouth is still the best way to discover new music, and Spotify offers many means for you to find and share your favorites. You can evangelize artists, songs, albums, and playlists on Spotify by posting them publicly or by sharing to a friend's Spotify inbox.
How to share music with followers on Spotify
On a Mac, click Share and then Post to Followers. Now you and your followers will see this info under Activity in the left sidebar. You can also post here to Facebook, Twitter, and Tumblr.
Use the same method to share music on Windows, iOS, and Android. However, to view Activity on a mobile device, you'll have to tap the menu button, then Notifications, and finally Activity.
How to share music directly with a friend on Spotify
To share directly to someone's inbox, both of you need to be following each other on Spotify, or you must be friends on Facebook and connected to Spotify via your Facebook accounts.
To follow someone, search for them on Spotify, select the person, and click the Follow button.
Now that you're following each other, you can share directly. On Mac or Windows, right-click the sharable item, then click Share and Send To. Input or select your friend's Spotify or Facebook username, and finally click Send.
You have more sharing options on iOS and Android. On iPhone, tap the three dots next to the item you'd like to share. Then tap Send To, then Select People, then search (or scroll) to find and select your preferred recipient, and tap Send. You can also share by email, text, or connected messaging apps, such as WhatsApp or Facebook Messenger. The process is identical on Android, except you'll be asked to Select Recipient instead of Select People.