Street photography comes in many different styles. In its broadest definition, it is any photo in which the presence of humanity is obvious. It need not have people visible. Even a photo of a house with a lawn chair in front of it can be considered street photography. Lee Friedlander and Robert Frank are two famous photographers who have a number of street photos without people in them.
Many idealize street photography as straight ahead shots of people at close range with or without fill flash. But that is merely one style that you can choose from. A fair amount of street photography is in this style. Bruce Davidson and Bruce Gilden are two examples.
The important thing in all street photography is that it is always candid. Which is to say that it isn’t staged or manipulated. A street photo is taken without the permission of the person or people in the shot. Asking if you can take their photo is more appropriately called street portraits. That is not a lesser form of photography. But it isn’t street photography.
In some countries, like Germany, it can be a problem to take a photo of a person without their permission. So full frontal shots of people is a risky business there. It is always wise to understand the laws where you are shooting street photography.
But you can also take photos of people from the back or as a silhouette, shadow or reflection. Photos in this style can leave much to the imagination. It is like visual poetry.
Have a look at the work of Saul Leiter for some examples of how to achieve interesting photos without a person’s face visible. He wasn’t shooting in Germany or facing that problem. Rather it was his personal style as a photographer.
Though street and documentary photography can overlap at times, they are two very different genres. With documentary you begin with an idea of what you want to capture beforehand. With street you work with what’s going on around you without manipulation. That said, there isn’t anything especially objective about either style of photography.
Street photography when done well is really a form of art. It’s a combination of timing and composition. And like the arts in general, it takes practice. The more you do it, the better you will become.
While you can learn much from books and videos, it is always about doing it. Taking workshops can be helpful. But you should really understand what will be taught and who is teaching it. Do they shoot in a style that you like? What kind of assistance do they offer? And do they have recommendations from a reliable source?
I work in multiple styles of shooting street photography depending on my mood and the weather conditions of the day. The more that you familiarize yourself with the many different styles of street photography, the easier it becomes to find your own style of shooting the street. Happy shooting!