Equipment :- Any camera can be used but if you are using a DSLR, a short telephoto range of between 85mm and 135mm tends to produce the most natural, pleasing results as it allows you to get close to the subject without being too intrusive.
Objective: - The objective of people photography is to reveal something about the personality of the subject(s) and perhaps about their life, interests or work. You don't want a stiff, formal pose that tells you nothing about the person. Family albums are filled with such photos of uncle Jack and auntie Jill. To take a good, interesting portrait you need to build up a rapport with the person and try to capture the moment when where is a spark of delight or interest reflected back at you.
Getting organized :- The last thing you want to do is keep fiddling with your equipment. People will soon tire of waiting to be photographed, so know your equipment and know where and how you want to photograph a person. Try to be in control but not aggressive. Be very aware of light and shadows, particularly on faces and if necessary, use flash to fill in shadow detail.
Approach :- Always ask if you wish to take a portrait of people in the street. Many will say no, but don't lose confidence, simply find another subject. In some countries people will ask for a small payment, so be prepared for this. Conversation or even gestures will help break down barriers. Openness is a great thing in people photography. And don't forget to say thanks and show them the result in your camera. You may also ask their details so that you can send them a copy.
Look for a clean uncluttered background or a background that shows how a person lives or works, e.g. a workshop, a garden or a living area. If working outdoors, try to have the sun at your side to avoid deep shadows (sun behind subject) or people squinting into the camera (sun in front of subject).
Photographing children is particularly difficult as they have a short attention span and get bored easily. If you can use a favourite toy or a pet to divert their attention. Soap bubbles, playgrounds or a ball are useful. Remember that children are small and toddlers are even smaller, so get down low to their level or even lower. Just follow them around rather than trying to get them to keep still, and take lots of photos. Remember to get parental permission and have a responsible adult or parent present when photographing children.
Teenagers are another problem as they really just want to play their video games or use their phones, so use that to your advantage. Perhaps simple props like musical instruments, surfboards, sports equipment, etc can help.
Photographing groups is difficult. Try to choose the location carefully and try to group people in loose pyramids
Technical :- On the technical side, a fairly shallow Depth of Field (see tips) will isolate the person from the background. Remember to focus on the eyes and the eye nearest to the camera in particular/ The eyes are the first place that people look in a photo and if they are out of focus then the image is weak. If a face is in shadow then you may be able to use a reflector (white paper) or fill-in-flash to lighten up the face.
Remember that you decide what is to be included in the photo. You may choose a formal head and shoulders, full face, profile or wideangle environmental shots.
I hope this helps. Just get out there and have fun.