1. You should have an account which allows you to do short selling.
2. 强制平仓: your broker needs the shares you have short sold
because the owner of the shares you borrowed wants to sell them.
or your broker thinks your margin is not enough.
Usually, if you short sell NT 1000 shares at $3.00, you need margin 3 X 1000 /2 = $1500
3. 佣金 is same as normal.