Ocimum basilicum has so many varieties it makes my head spin. Each variety has a distinctive leaf type and scent profile. Most are annuals, or are grown as such. I've heard that basil can be grown here as a perennial, but my experience says "annual". Maybe in the true tropics, it grows all year.
For the last several years, I grew only Thai Basil (var. thyrsiflora). This year, I got hold of some Lime Basil seeds, which can be hard to find. I also found Spicy Globe Basil, Columnar Basil, and Cinnamon Basil. They are all growing beautifully and my cooking has really gone up a notch as a result. Here is the gallery:
All the basils need plenty of sun and water. Here in Zone 9 (subtropical), they need refuge from direct afternoon sun and heat. I keep them in a west-facing, covered patio, and in a north-facing alcove. That way they get either direct, cool morning sun, or indirect afternoon sun. I water daily and use a well-draining soil, but their schedule will depend on your climate zone and soil type. I use a general fertilizer once a week. They'll flower in late summer (harvest and save the seeds for next season!), then die back in November or December.