http://sheldonbrown.com/derailer-adjustment.html Worked for me. B and C seem to be your limit stops for the rear. D/E you can forget for the moment, as long as the chain is able to move to smallest/biggest sprocket without hindrance. Ensure before you jump to conclusions that You haven't bent the RD or its hanger; Your cables are tight when they should be and slack when they should be; Your FD hasn't slipped and changed position, making it hard for the chain to reach.
