I am curious how others initiate a credit spread. Do you begin with the debit part first and then proceed to open the credit portion? I am going to use IB and I'm not sure how they will calculate margin requirements if I open a naked portion first. Also, do you hit the ask or bid or sit on both portions until filled? Options are supposedly first come, first serve. Would it be more advantageous to open an OEX credit spread or options on ES?