For broader overview of Modern art (since about 1900 or the impressionists on) Robert Hugh's series Shock of the New is a good place to start. I remember watching as a student. For an introduction to more contemporary art and artists who are working today, the PBS series ART 21 is also pretty good.

Mainly just look at things and stay open minded an inquisitive. Recognize a lot of art is more about inducing questions than transmitting a specific message you are supposed to "decode". As a viewer its your job to make connections to your own experience/place in the greater culture at large and complete the work so to speak.

There is no right or wrong answer.

Enjoy.

A good start, check the museums themselves for tours, free classes and the like. Many have a lot of educational information available, starting with info for beginners, all the way up to experts.