Surround the fire pit with non-flammable material such as pavers or gravel to provide a level seating area and to protect plantings from catching fire.
Choose plants that look interesting in the season(s) that you most use the fire pit. Ornamental grasses and late-blooming native perennials, such as ironweeds (Vernonia spp.) and black-eyed Susans (Rudbeckia spp.) are good choices for fall. As with all fire-pit plantings, be sure to take into account their mature size and site them well back from the fire.
Choose plants with variegated or light-colored foliage and/or light or white flowers. These will show up best when the fire pit is used in the evening. This might be a good place to try making a white garden.
Enclose the area with a ring of shrubs to create a secret and cozy spot. Be sure to leave a clear exit somewhere in the ring.
For safety, create safe, smooth walkways to/from the fire pit. Line the path with lighting or keep flashlights handy for trips to and from the fire. Keep a bucket of water or sand, a hose and/or a fire extinguisher nearby when the fire is lit. Before creating a fire pit, check with local authorities for any regulations regarding outdoor flames.