In many ways lighting is the key to photography. There will be numerous Tips & Techniques dedicated to the subject, but for now I really want to draw attention to two types of lighting at opposite ends of the spectrum, and make the point that it is possible to take fantastic photographs with the simplest of compact cameras whilst introducing the benefits that more sophisticated lighting systems can add.
Many different types of lighting are suitable for boudoir and nude photography. Your choices will be governed by the camera you use, the space available and your budget.
Studio flash offers the most versatility and control, but it is expensive and requires a camera with a 'hot shoe' flash connector as a minimum - something not found on many compact cameras.
The advantages of studio flash stem from the fact that they are
a) away from the camera. On-camera flash introduces problems with red-eye and gives lighting that flattens facial features too much. They can also cast a nasty shadow of the subject on the background.
b) can be used in multi-flash combinations, with accessories such as soft-boxes to precisely achieve the results you desire.
The image below shows a typical 3 head setup: two large softboxes in front of the model cast a soft flattering light at about 45 degrees to the camera and a brighter 'hair light' behind the model adds depth and more contrast to the shot.
Available to everyone for free, daylight is the obvious choice for anyone shooting on a budget. Shooting outdoors can pose some problems when the sunlight is too harsh, but these can be easily overcome (subject of an upcoming Techniques article).
Indoors, the light through a window offers a soft, flattering light which is fabulous for all types of indoor photography.
The picture below was taken solely by window light. In this case there was sufficient light to shoot hand-held at f5.6, 1/100th second at ISO 400.