# To ssh via pem file (which normally needs 0600 permissions):
ssh -i /path/to/file.pem user@example.com

# To connect on an non-standard port:
ssh -p 2222 user@example.com

# To execute a command on a remote server:
ssh -t user@example.com 'the-remote-command'

# To tunnel an x session over SSH:
ssh -X user@example.com

# To launch a specific x application over SSH:
ssh -X -t user@example.com 'chromium-browser'

# For more information, see:
# http://unix.stackexchange.com/q/12755/44856