How to know where the coast is either flat or cliff?

In a basic geography (if I recall correctly), there are two main types of coast, flat ones like the beach and cliff ones with the rocky terrain.

I always wonder how to know where is those types of coasts are located without having extensive knowledge of the map area. Like for example England, how do I know which coast is rocky and which coast is flat when I don’t have knowledge of the country itself.

Also bonus question: how do I know which part of the coast is deep sea like port area or shallow sea like the beach?