Notice the differences between yourself and what you are trying to be. Even if the change in façade may not be entirely different from who you are, noticing the subtle changes will help you to emphasize them when the time is right. Outline what makes the façade and take note to embellish those qualities later.
Look the part. A change of clothes can work miracles on how other people perceive you. Sometimes to change façades, it is necessary to literally change clothes. Make sure that what you wear is a representation of the stereotypical façade change you are making.
Vocalize the façade. Just as actors sometimes have to disguise their voices for a role when they take on a different persona, changing façades sometimes means speaking the part. If the façade is louder for instance, speaking with a pronounced or more confident tone can make the sudden change for you.
Imitate the real deal. One of the biggest things you can do to help change façades is to copy someone who you feel embodies what you are trying to portray. This can be quite difficult if you aren't a good actor, but this is a process that's done over time. Immersing yourself in the culture of someone who you are trying to be will help you to better relate to the façade.
Draw from your own emotions. As human beings, we have the ability to feel a variety of emotions. Everyone has the ability to be crazy, happy, mad, sad, hurt or elated and sometimes these can be experienced at the same time. Drawing on these emotions and incorporating them into your façade change will make it seem more genuine and give it a real undertone.