I am going to install Ubuntu on a new computer, but I'm not quite sure how big each partition should be.

If I create only root, home and swap partitions, on what partition will programs be installed? Will they go to /home or to root?

Basically does it make sense for instance to have following partitions:

    /     - 6GB
    /home - 80GB
    /swap - 4GB

Is 6GB large enough for my root partition?

Also are these 3 partitions a good choice, or is there a better configuration?

I have at the moment 3 operating systems installed, and I do make changes quite often.