Taken from Navigating Postgresql with Psql Command Line – 10 Simple Commands and YoLinux Tutorial: The PostgreSQL Database and Linux
\l # List databases
\c database-name # Connect to database
\c # Show the database your are connected to
\d # List tables in database
\d table-name # Describe table
\e # Edit current command
\z # list permissions for current user
\q # exit psql
\h # get psql help
SELECT * FROM table-name # List table contents