Street photography is all about capturing emotion, humanity and soul. There are lots of stories out there waiting to be told.
Telephoto lens street photography
The most common argument you will hear is that these type of lenses allow you to keep a distance between you and your subject in order to be inconspicuous. Experienced street photographers will rarely approve the use of telephoto lenses. If you dare call yourself a street photographer, don't ever let fear stop you from approaching your subject if possible.
Candid street photography
It focuses specifically on getting your camera as close as possible to people without them noticing. It helps to catch scenes in an uninterrupted fashion. And if you happen to get caught then so be it, just smile and own up to what you are doing. You will be surprised how many people are understanding if you are honest with them.
If you see a good street photography scene take more than one shot. Even Henri Cartier-Bresson took 20+ photos of a single scene if he thought it was interesting enough. By taking multiples shots, you have a better chance of capturing that perfect facial expression, hand gesture, action or movement that turns the picture into a decisive moment.
When shooting strangers you have a much better chance to end up with a strong and excellent portrait, if you engage in a conversation with the person. Ask permission to take a portrait so they are more at ease with the process. If you ask permission and it is granted, take your time. Show them the pictures on the back of your camera and tell them why they caught your attention. Everyone enjoys a compliment.
Whatever your technique is, remember Robert Cappa's quote:
“If your pictures aren't good enough, you aren't close enough."