Jim Willis wrote:
Hi folks... I know next to nothing about bicycle maintenance, so this
should be a very basic question... what is wrong with my bike if it is
really difficult to shift speeds and when I try to it keeps making
that awful buzzing/clacking sound? I am a pretty quick learner... how
can I fix this myself without having to go to (and thus pay) a
mechanic?

Read the following instructions and have a twiddle. Good luck.

http://www.sheldonbrown.com/derailer-adjustment.html

http://www.parktool.com/repair_help/FAQindex.shtml

~PB