when I try to login to my database with psql, doing this:
psql dbname --username=qgis --password
>>(prompts for password, entered password)
psql: FATAL
You need to grant a privilege. Try this:
psql dbname
>> GRANT CONNECT ON DATABASE dbname TO qgis;
I assume you will also need further privileges. PostgreSQL has one of the best documentation pages of all the DBMSs: http://www.postgresql.org/docs/9.0/static/sql-grant.html (You can choose the postgres version you're using at the top of the page).