Answer:
To remember the difference between "capital" and "capitol," it may be helpful to think of the following:
"Capital" usually refers to a city that serves as the center of government or commerce, such as Washington D.C. or London. It can also refer to a form of wealth, such as financial assets or property that can be used to generate income.
"Capitol" usually refers to a specific building or group of buildings where a legislative body, such as a parliament or congress, meets to conduct business. In the United States, the Capitol is the building in Washington D.C. where the U.S. Congress meets.
One way to remember the difference is to think of the "o" in "capitol" as representing the dome of a building, such as the dome of the U.S. Capitol building in Washington D.C.
Another trick is to remember that "capital" has an "a" in it, and "a" can stand for "all" or "assets," which relate to the financial meanings of the word. "Capitol," on the other hand, has an "o" in it, which can remind you of "only" one specific building.
Ultimately, practice and exposure to the two words in context will help reinforce their meanings and uses.