Keyboard shortcuts:

• ^n (Ctrl+n) -- Compose new Twt
• Esc (Escape) -- Close the composer
• ^t (Ctrl+t) -- Refresh or navigate to Timeline
• ^m (Ctrl+m) -- Refresh or navigate to Mentions
• ^d (Ctrl+d) -- Refresh or navigate to Discover

There are shortcuts for Feeds, Settings and Profile too (similiarly))