In addition to the ones described by mook,
I think the crossed arms position is a decent ready position. Not with the arms weaved inside one another but loosely held in front of the body. This can very quickly become lan sau, fak sau, etc.
I copied this from my facebook page on this very topic :
Many martial artists think that if they adopt a strong fighting stance when they're confronted, their opponent will see that they are a formidable adversary, and possibly back down. But that's not always the best tactic to apply in the initial stages of a confrontation.
Why not? Well in terms of body-language, a fighting stance is an aggressive statement... a threatening gesture. So when one person adopts a fighting stance, the other person will often feel compelled to adopt a fighting stance as well, to either protect themselves or to save face.
This is why adopting a fighting stance in the early stages of a confrontation can actually escalate the level of violence - unnecessarily. And you might find that the law in most places requires you to retreat from a potentially violent confrontation if possible... and standing your ground in a fighting stance doesn't demonstrate any attempt to do that. In fact it shows just the opposite; you are entering into the fight of your own free will.
Also, adopting a fighting stance informs your opponent that you have some level of training. This could cause them to adjust their attack strategy, use a weapon, or call for back up.
In fact, if any of your opponent's friends think that your fighting stance makes you look too threatening, these days they're just as likely to step out of the crowd and hit you over the head with a bottle.
In the video, (
http://youtu.be/sDyQKzLysro) the WT fighter has adapted his stance to look non- threatening. This doesn’t tip his hand to his would be attacker. It may cause the aggressor to back off if he sees that you don’t want to fight. It gives any onlookers the appearance that you didn’t want any part of this.
All while still having your hands on your center, poised and ready for action.