If you are trading CFDs, you just open a short position as you would a long position. If you want to short actual shares which you own, you must borrow shares from your stockbroker to begin a short sale. The availability of shares for short selling depends on the access and interconnectivity of the broker across the financial system. Brokers that cater to institutional clients have the most competitive short-selling conditions, but smaller retail brokers offering highly liquid assets can efficiently facilitate short sales across their internal order book.