Shirakawa-minami Dori is regarded by many as Kyoto's prettiest street. I think it's best during the Sakura blossoming time, especially when the flowers are lit up in the evening. However it's a great place to visit anytime of the year, although before 11am it's pretty quiet and many of the shops are shuttered up.
It's also a place where you may spot a genuine Geisha (rather than just a tourist paying to dress up as one). They'll either be visiting the Shrine (known as "Tatsumi-jinja") at the eastern end of the street or on their way to entertain clients at one of the expensive establishments along the street. Either way you'll need to be fast on the shutter button to catch a photo of them, as the real ones don't stop to pose for tourists.
Other than Geisha, it's also a popular spot for wedding photos, so you may be able to see a Japanese couple dressed in traditional Shinto wedding attire, especially on weekends. I've also met people there who dress up in Kimono as a hobby, congregating there just to look the part. Make sure you visit Shirakawa-minami Dori during your stay in Kyoto, it's an unforgettable experience.
Most of the restaurants along Shirakawa-minami Dori are pretty expensive, but worth considering if you want the authentic Kyoto high class dining experience. For those on a tight budget there is at least one cafe on the street with reasonable prices or just bring a bento and sit down under the big red umbrellas at the western end of the street.
Shirakawa-minami Dori is in Gion. The western end of the street is near the Kamo River (Kamogawa) between Gion Shijo and Sanjo stations on the Keihan line. It's also not far from Kawaramachi station on the Hankyu line or the Sanjo Keihan station on the Subway Tozai line.
This photo was captured with a Nikon D700 camera and an AF Nikkor 50f/1.8D lens. This is the jpeg straight from the camera, no post processing has been done on this image.