For those in desperate need, I have provided a few hints. Best to try without them first, then if you are really stuck, read them in order until you are no longer stuck.

hint one
hint two
hint three
hint four
hint five
hint six

There is also a complete walkthrough. It can even be played in game via the 'replay' command. Note that this is far from the only way to complete it, and should give you some ideas for further solutions if you are interested in that type of thing.