When writing addresses, use commas to separate street from town and town from state.

Here’s the easy rule about capitalizing place names: if it appears on a map, it should be capitalized. Regions, states, cities, streets, highways, parks, buildings, monuments, mountains, rivers, coasts—capitalize all of them.

Nicknames for places usually get capitalized.

When writing the name of a city and a state, surround the state with commas if it’s an abbreviation.

In formal writing, states’ names should be spelled out.

There are two systems for abbreviating state names. The first uses lowercase letters and periods: Minn. for Minnesota, N.Y. for New York. The second is the two-capital-letter system used by the post office: MN and NY. Either system is fine, although only the second should be used when postal addresses are involved.