First day trading on thinkorswim I tried to short APOP at $5.86 which  would have turned out to be a great move. But come to find out thinkorswim does not allow short trading on accounts with less than $2,000. I set my stop loss at $5.90 and so it turned out that I bought shares instead of selling them and then the stock plummeted. Ended up getting out at $5.20 with a 7% loss so nothing too crazy but now I know.