One simple way to differentiate NPCs and locations is by naming them uniquely. One easy way to do this is to start each one with a different letter of the alphabet. It makes it easier for people to distinguish two names if they start with unique letters.
If I see two NPCs, named Sean and Seth, I find I can confuse the two, especially if they are not NPCs I interact with a lot. By changing up their first letter, Sean and Jeth, my mind compartmentalizes them into a different alphabetical partition, making it easier to keep them separate.
If you find yourself running low on unique letters you can start to use a digraph; two consonants brought together to make a unique sound, such as BRing, SLide, STeve.