How to transfer movies to my Apple TV?

Personally I don't recommend this and would suggest an external drive to house your itunes library for your laptop, however you might want to read THIS

How? you place your movie files on some disk of your choice, point itunes to it then point ATV to the computer which governs itunes. Sync what you can hold. You best have a good backup. Once you delete the files from the computer and re-sync, which is too easy to fall into then your synced movies will be gone.

DO NOT HAVE YOUR FILES ONLY ON THE APPLETV! I have had to reboot and delete all my files too many times to get the aTV to work. You would lose all your files this way. Use the external HD for your movies.

as others have said keeping your files ONLY on appleTV is not a good idea... and not it's intention... appleTV is still sometimes flaky and may need to be reset at time... without the files also on an external drive somewhere you will kiss your files good bye... also you can't get the files off of the appleTV if need be without taking the appleTV apart, removing the HDD and attaching it to a computer or hacking it... both of which would void your warranty

in the case of a laptop.. airport extreme with attached USB drive or time capsule are good options as they allow for wireless connection to external... also remember that unless you can afford to lose everything on your drive you should in addition backup i.e. time capsule with USB drive attached or airport with two drives attached... one for storage and one for backup... you can get 500GB drives for $70 these days... is it worth taking the chance you lose everything on your computer over $140?

just press the *option key* as you are dragging the file into the "library" in iTunes and the file will be added to the iTunes library but not copied there (basically a path to the file gets added)... this way you can leave the "Copy files to iTunes music folder..." setting alone and just do this on a file by file basis.