Making a map look realistic only requires a very basic understanding of physics and geography. Fantasy Geography doesn't have to stick to rules - but it helps to think of Earth's geography for realism. Is your world on a globe-shaped planet? If so, then it might have an equator, or poles that are colder or warmer - so you would put deserts in the middle where it would be hottest, and ice at the very top/bottom where the temperature is coldest.
It is helpful to think of all of the things that contribute to the shape of landscape, including mountains, beaches, rivers and even deserts as controlled by Weather.
Weather is caused by the height and density of mountains: where clouds gather, winds are formed and rain runs down and forms rivers. Rivers usually start at the base of a mountain and make their way out to sea by following the path of least resistance or a downward slope. Rivers turn into lakes when they are trapped by the landscape and pool or flow and split into smaller estuaries out into the sea when not.
Terrain pushes right up against other terrain types in realistic geography with plains separating climates and terrains such as jungle, forest tend to form around mountains where there is a lot of water. Desert can form anywhere.
Erosion of mountains leaves behind cliffs which turn into rocky surfaces and eventually sand on a beach when erosion is at its highest and the rocks are strongly tested by the salt waters of the ocean and exposed to wind.
Large Towns are generally near plentiful water sources and sources of wood for building - forests in particular, or bays/coastal areas ideal for trade and commerce. Smaller villages can be anywhere as they usually have a brook, well or spring to take care of their water needs.