Troubleshoot a PostgreSQL "Could not connect to server" Error

Learn how to troubleshoot one of the most common PostgreSQL errors, "Could not connect to server." There are several different variations of this error. [...]  

Solve the PostgreSQL Error "psql: FATAL: database "root" does not exist"

Learn how to solve the common PostgreSQL error psql: FATAL: database "root" does not exist." New PostgreSQL users often encounter this error when first logging in to PostgreSQL. [...]