When hosting a party it is best to coordinate the flowers with the theme of the occasion. For a rustic summer bbq you might have wild flowers in mason jars or for a baby shower, soft pastel colors would be sweet. If there is no theme to your party, then choosing seasonal flowers to best compliment your homes color scheme is the way to go. If it's spring indulge in tulips and if it's fall dahlias are always fun.
A client of mine recently hosted a "Thai dinner " evening. Orange calla lilies, yellow cymbidium orchids, yellow pin cushions and bamboo accents were chosen to add some asian flair.
Give your guests something to remember. Small details like flowers at each place setting are sure to be appreciated by most.
(bird of paradise could be seen by guests in the living room next to the dining room)
Be sure to put flowers in all the rooms your guests will frequent. I think everyone loves to be greeted in an entry with flowers. And my personal favorite room for flowers is the bathroom. Because usually all it takes is a single stem!
Good luck with all your future party planning.