Firstly, feathered wings would be a nightmare on humans, mainly cos we're naturally not feathered. We have skin, and so our wings should also be covered in skin, yep, like a bat. Otherwise, you'd have an overload of biological and logistical issues, like how can the winged human take a shower/bath with soap? The feathers would get gummed/ruined. How would the blood circulation in the body work out? And what happens if the human falls down in mud on a rainy day? Mud would cake the feathers... So to be realistic, skin-covered wings would be better for humans. Also, the wingspan would have to be very long. About 15 feet from wingtip to wingtip for the average-height human adult.
How best to connect it the body, well, it would be better if it connected directly to the spine, like all our other limbs. So maybe the wings could connect either directly in the middle of the back or spaced slightly apart (but must be between shoulder blades, otherwise arm movement would be impeded). The connecting area between the wing and the back could be from shoulder-height down to maybe mid-back or three-quarter ways down. Any less and the wings would be liable to tearing off when faced with a strong force. Blood circulation would, of course, have to include the wings.
As to hiding it on a day-to-day basis, the best way would be if you could draw out a design for your wings so that it can support the human's weight, and yet it can also fold neatly along the back. The batwing design would be a little difficult here because the long 'fingers' make it difficult to fold easily. You can see a picture of man's arm, bird's wing, and bat's wing here. What would be ideal is the skin-covered wing of a bat, but with the bone structure of a bird. Windbreakers with special slits in the back can be used, so that the wings can be hidden while the jackets are worn, yet in an emergency, the wings can snap out of the slits.
With regards to adaptations in the human body, of course, the bones would need to be lighter. Maybe not hollow, because our skeleton would need to still support our bodies, significantly less dense. Muscle structure, also less dense, and the human must have very little fat or he/she'd be lugging around a lot of extra weight. Heart compressions must come faster to support the beating of the wings (which need to be very strong), and so diets would need to change too. On average, the human-bird would need maybe twice to three times as many calories as a normal person. Also, birdlike air-sacs in addition to lungs would be very useful, as well as something that may allow them to breathe in the lower-pressure atmosphere when they fly. Basically, the human has to be as light as possible, and yet strong.