Needless to say, during the eclipse no surface features will be directly visible as the Moon will appear completely dark. However, if the eclipse is total and you are lucky enough to be in the path of totality, you will see a phenomenon caused by the Moon's topography. Baily’s Beads are a string of lights at the edge of the Moon’s disc immediately before the Sun disappears completely and just as it begins to return. They are caused by the Sun shining between the lunar mountains along the limb. There will be a moment when there is only one "bead" - this is known as the diamond ring.
There are other interesting and unusual things to look for. When the Sun has been reduced to a thin crescent, look at the ground beneath a tree. You should see many tiny crescents, caused by the gaps between the leaves acting as pinhole cameras.
During the last ten minutes before the total eclipse, you might cover one eye to improve your sensitivity to the darkness when it arrives. This will make it easier to see the patterns in the Sun's corona (the faint outer halo which is usually invisible) and prominences (which look like tiny flames coming from the Sun but are actually huge eruptions thousands of times larger than the Earth).
During the first and (particularly) the last moments of darkness, look at the ground. With luck, you may see an elusive effect called "shadow bands" - a rippling light caused by the uneven density of the atmosphere, rather like the dappled light on the bottom of a swimming pool. A large white sheet of paper spread on the ground may enhance the effect.
One vitally important note: never look directly at even the tiniest portion of the Sun's disc. Either use a pinhole in a piece of card to project the Sun's image onto another piece of card, or use a proper eclipse viewer (this should filter out all UV and infrared radiation, should pass no more than 0.001% of visible light, and must have no nicks or scratches). Only when the Sun is completely hidden is it safe to observe without protection.
Several articles about eclipses appear in Inconstant Moon's reference area Cyclopedia Selenica. Details of eclipse times and locations can be found in the Inconstant Moon Diary.