basically - my setup is an imac on a wireless connection. so normally - for transferring a few files i just leave it as is and transfer at G speeds. If i have a large amount of files to xfer i do the following.
on the imac i go to settings / sharing then select internet sharing. say START
where it says SHARE YOUR CONNECTION FROM : you must select ETHERNET
Now if your mac is connected tot he internet with an ethernet cable - good for you - if not - you will now lose your connection to your wireless router.
then for TO COMPUTERS USING: you check AIRPORT
click on AIRPORT OPTION to assign your wireless network name and a WEP passcode etc.
click OK and make sure the internet sharing is enabled.
now - have your appletv scan for wireless signal and you will see your new network. connect to it. it might take up to 1 minute - i thought my apple tv froze but it will connect.
now - u should check the assigned ip address of the apple tv, i think it will be like 10.x.x.x
i can then ssh or ftp into that newly assigned ip address.
voila - N speed 5.5mb
when i am done i just disable the internet sharing and it reconnects to my wireless g router.