Here’s why sketching candid portraits is a super-fast way to get good at sketching well:

• It forces you to sketch quickly – people can move at any time!
• It gives you a chance to sketch lots of different types of people – from different angles
• It puts pressure on you to draw well – people around you can see what you’re drawing! The person you’re drawing might want to see!
• It’s free (well other than the cost of the train or the cup of coffee, or whatever incedental costs you incur in a public place)
• You can do it on your way to/from work – or any other time you’re on a subway, bus, waiting for your food at a restaurant, etc.
• It’s fun!