You never know what someone has gone through during the day. They may be struggling with a loss, elated due to great family news or have been fighting traffic for hours.
Instead of coming on strong and being bubbly for the sake of being bubbly, match their personality and body language. Being on the same page as someone builds a level of comfort that is hard to achieve elsewhere. This is a sales coaching tip that works over the phone or in person with just a little practice.