Generally flooring like this is laid along the longest wall. If there isn't one, it's up to you. Just make sure you measure it out beforehand so you won't end up with a last plank being 10cm or something. Same goes for the width. If you end up with the last one being a few cm, it's better to start with half a plank.
Think about what room it might carry over into. Laying it short way in a small room can look weird while it's not as noticeable in a larger room with furniture.