From such an application simply type help or ? to get a list of all the FTP client commands:
ftp ftp> ? Commands may be abbreviated. Commands are: ! cr macdef proxy send $ delete mdelete sendport status account debug mdir put struct append dir mget pwd sunique ascii disconnect mkdir quit tenex bell form mls quote trace binary get mode recv type bye glob mput remotehelp user case hash nmap rename verbose cd help ntrans reset ? cdup lcd open rmdir close ls prompt runique
To find out more information (though dont rely on get a lot of help) you can type ? command
ftp> ? help help print local help information ftp>
Remotehelp from the server can be obtained in a similar fashion:
]-- Request help from the remote FTP server. If a command-name is specified it is supplied to the server as well.