just lay in front of the dozer, dont' move no matter what.
then you end up following Ford Prefect to the pub. go to the mens room and piss, then you like pass out or something, then you get this cheese sandwich or you give it to some dogs or ants or something.. then you go back to your house to see it destroyed and you get taken up onto the Vogon ship, then you get the babelfish.. I could go on and on. I beat this game yeeeears ago
there is a walkthru somewhere, that tells you exactly what to do in case you get stuck. Just wait till you get on the ship and you have to get the Babel fish! That was so notoriously hard, back when this game came out, there were actually t-shirts that you could buy that said "I got the babelfish!" :Q
that brings back memories to infocom text adventure games on my PCjr when I was like 10-12... wow