Special characters in SQL queries

First a single quote in text, when a backforward slash in a file path, what other special characters need padded in two 
backslashes before using the data in a SQL statement?

After hours' search in the PostgreSQL archive, I find a releted information on the http://www.ca.postgresql.org/users-
lounge/docs/7.2/postgres/arrays.html.  It's about array data though.

How can I find out those characters so that I can pre-process them before a SQL query?

Thanks for your information.

Vernon