Open body language promotes a more open and agreeable response. That means uncrossing your arms and legs. Crossing your arms and legs creates both a physical and psychological barrier, which can set up a defensive posture on the part of the person you’re trying to persuade.
Most women, however, are more comfortable sitting with their legs crossed. If this is the case with you, then make sure that your legs are crossed towards the person with whom you’re speaking. That shows that you’re more agreeable, and will help you get what you want.