Choose a centerpiece you can talk across
Let the arrangement sit below the conversation rather than between two faces.
The nicest flowers on a dinner table can become a nuisance as soon as people sit down. A tall vase seems modest when you stand over it, yet lands directly between two faces at chair height. Before deciding what to arrange, sit in the seats that will actually be used and look across the table.
A low bowl is often easier to place than a narrow, tall vase. Its footprint still matters: a wide arrangement can quietly use up the room needed for a serving dish. Set out plates, glasses and the largest bowl first. The space left between them is the space available for flowers, not an invitation to squeeze everything together.
Think in small separate pieces
Three small vessels can be moved individually during a meal. One large arrangement cannot. On a long table, a few separated clusters leave useful gaps for bread, water and hands. They also let guests at the far end see a detail without requiring a continuous runner of greenery.
You can make the pieces relate through a single material. Small clear glasses do not have to match exactly, and a group of plain ceramic pots can accommodate slightly different shapes. Keep the visual decision simple if the table already has patterned plates or a strongly colored cloth. Otherwise the flowers may become another competing pattern.
Avoid letting stems, leaves or decorative objects overlap eating surfaces. The arrangement should stay in its own area rather than hang over the edges of plates. Keep strongly scented displays away from the food, and choose a stable vessel that will not rock when a dish is passed beside it. If you use candles, leave the clearances required by their safety instructions; flameless lights remove the need to fit an open flame among flowers.
There is also nothing wrong with an empty center. At a shared meal, the serving dishes can provide all the shape and color the table needs. Put the flowers on a sideboard where people can enjoy them on arrival, then let the table become part of the evening instead of a display that everyone has to work around.