I was unable to find the correct Ubuntu package for PostgreSQL 9.3 for Linux Mint 13, so I installed from source. The server comes up just fine, but when I try any command from the command line, I an error--for example:
./createdb test2
createdb: could not connect to database template1: could not connect to server: No such file or directory
	Is the server running locally and accepting
	connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
I read a posting that said such an error can be avoided by adding a '-h localhost' argument, and indeed the following worked:
./createdb -h localhost test2
How can I eliminate the need to add this additional argument all the time?