To mirror a website and do some sophisticated FTP commands, check out lftp
To mirror a directory, cd to local directory first and then do the following:

$ lftp [email protected]
lftt> cd <directory_as_appropriate>
lftp> mirror -R -e -v -n (use --dry-run to just list files)

-R puts files from local machine to remote machine
-e deletes files on remote machine that aren't on local machine
-v is verbose mode
-n transfers only new files

Other tips:
http://tutorials.papamike.ca/pub/lftp.html