u would constrain it to a joint so that it moves when the body moves. in your case y can control the direction the knee is pointing with the locator polevector constrain. to parent it to a join (usually the root ) select the locator and the joint then press p.
for the difference between the 2 types of solvers for the ik, u can read up on the manual or help file that came with maya.
i prefer to use sc on legs and rp on arms... makes things eaiser to switch back and forth to fk. not the best rigging method though...