Depending on the number of guests and your venue, centerpieces can be the single largest expense in your flower budget. Centerpieces are also an important player in giving that festive occasion feel when you enter the venue. In my experience the most common mistake is not paying attention to scale and proportion. A 6 foot round table has lots of real estate in the middle that can be used to create that festive feel. If ceilings are high you can go high.
With this centerpiece the flowers are not blocking the guests