A good sensor, fast glass, steady hands, a good flash and a tripod. Or any combination thereof.
What is the occasion ? How close/far will your subjects be ? What type of quality image are you after (eg how much noise is acceptable) ?
Keep it simple. Also recall that you have a triangle; ISO, Aperture, Shutter speed. My personal choice is to maintain a shutter speed I know can reasonably stop subtle motion and handshake. Grain from higher ISO, I can work. Shallower DOF from faster aperture I can work via composition. Blurry pictures... no can do. A clean, noiseless, well composed photo will still fail if the subject is blurry (unless intended) from motion or handshake.
And usayit, I would love to start learning a little bit about flash. That's probably the one thing I know NOTHING about I photography.