This was very good advice from Child of the Light in the Energy Work forum- what to do before someone brings yucky energy to your house:
viewtopic.php?f=20&t=21770#p140720

Excerpted:
placing white flowers or carnations in the guestroom before the person arrives. The white flowers are said to 'absorb' any negative vibes the person may be have and leave behind, and then a thorough smudging is the home is to follow to remove any lingering 'bad vibes.'