Do a search for metaballs on the forum. Lots of examples from a few months ago. Right now I'm working on a human character using metaballs. Metaballs are spheres which when rendered "melt" into each other, the amount is determined by the objects bounding box (i.e. if both balls are outside of each other's bounding box no "melting" occurs). To get negative metaballs (since they can't be booleaned) hold down shift while clicking on the create metaball icon. Grouped metaballs will not interact with other metaballs, only those withing the group will interact. That's about all the basics I can think of.