The surface of Mars is classified into two types of regions, the lighter red-orange regions covered with rusty dust and the darker regions which are large areas of exposed volcanic rock. During early days of telescopic observation, the light regions were thought to be continents so they were given names that described land masses. Major regions of this type include Elysium Planitia (the Elysium Plain), Arabia Terra (Land of Arabia), the circular Hellas Planitia (Plains of Greece), and Amazonis Planitia (Amazon Plains).

The darker regions were names after seas, lakes or other watery features. So there is the very large Mare Erythraeum (Arabian Sea) in the south, Mare Acidalium (named after a legendary fountain) in the north, and most strikingly, the large wedge-shaped feature Syrtis Major named after the Gulf of Sidra off the coast of Libya. Syrtis Major is the most obvious dark region on the Martian surface. Many of these dark regions appeared to early telescopic observers to change size during the Martian year. They suspected this was caused by changes in vegetation or rainfall. It turns out the dark regions do not change their dimensions, but instead occasionally are obscured by atmospheric dust. The imaginative 19th-century astronomer Percival Lowell noted the region called Solis Lacus (Lake of the Sun), just south of what we now know to be Valles Marineris, an enormous valley as long as the continential United States, seemed to wax and wane with the seasons. Lowell observed many (illusory) canals converging in this region and speculated it was the capital of the Martian civilization. Solis Lacus is a part of what's now called Solis Planum. Observers often remark that these dark regions appear green. They are not… they are grey-brown and simply appear green because of the contrast with the red-orange surroundings.

In some images of Mars from space or from Earth-based telescopes, whitish features are visible. These are usually cloud formations. They are associated with low-lying regions where clouds collect, or in the vicinity of the peaks of volcanoes where warm air rises up the side of the mountain and condenses into clouds.

The key features to look for on Mars with a small telescope include:

The arrow-shaped dark region of Syrtis Major

The southern dark features including Mare Tyrrhenum, Mare Erythraeum, and Mare Sirenum; also look for the circular reddish-orange feature Hellas

The broad ochre regions of rusty sand marked by Arabia and Eden Terra, Tharsis and Arcadia, Amazonis, and Elysium, all of which are at equatorial and temperate latitudes

In the north of Mars, look for the dark areas of Utopia Planitia and Mare Acidalium

And of course look for the polar caps. At a glance, you will immediately see which polar cap is most easily visible

Sky and Telescope magazine has a useful Javascript tool to help you see what is currently visible on the face of Mars, assuming such features are not obscured by a Martian dust storm. You can access the free tool at this link (free registration may be required):

http://www.skyandtelescope.com/wp-content/observing-tools/mars_profiler/mars.html

In this tool, you specify your time of day and date, as well as your preference of view to match your telescope: inverted (like with a Newtonian telescope), mirror reversed (as with an SCT/MCT/refractor with a star diagonal), or direct view (with an erect-image telescope… not a common situation for astronomers). Then this Javascript tool generates a small map to show you what to look for. It also gives you the expected apparent magnitude, diameter (in arc-seconds), and other data. This application also assumes you're observing from Earth's northern hemisphere, where the north pole of Mars points toward the north direction in the sky. If you're in the southern hemisphere, then this image must be inverted again with the controls.