Put up a small sign telling passersby what you do and for how much. Put a couple of plastic chairs in front of you and set up a small easel. Get yourself a 'shill' for the first bit, a friend who will pose for you as you sketch.   Do several sketches of your friend from different angles. If you're good and it's priced right, people will respond.

Suggest a special rate for sweethearts or children or parent and child. Remind people of the intimacy of a drawing. Suggest a drawing as an ideal gift.

Be friendly. Smile. Be open to answering questions. Commit to being in the same spot at least a week, so people can make a mental note to return.

Good luck.