I feel the need to set the record firmly crooked.
Douglas Adams has, in fact, published the final, comprehensive
Hitchhiker's Guide under the title "The Ultimate Hitchhiker's Guide." In the introduction (A guide to the guide) Adams points out that there are so many different versions of the series that he contradicts himself everytime he re-tells the story. In this definitive edition he "sets the record straight, or at least firmly crooked." It is in this introduction that Adams gives the instructions to leave the planet. They are as follows:
1- Phone
NASA. Their phone number is (713) 483-3111. Explain that it's very important that you get away as soon as possible.
2- If they do not cooperate, phone any friend you may have at the
White House -- (202) 456-1414 -- to have a word on your behalf with the guys at
NASA.
3- If you do not have any freinds at the White House, phone the
Kremlin (ask the overseas operator for 0107-095-295-9051). Thye don't have any freinds there either (at lease none to speak of), but they do not seem to have a little influence, so you may as well try.
4- If that also fails, phone the
Pope for guidance. His phone number is 011-39-6-6982, and I gather his switchboard is infallible.
5- If all these attempts fail, flag down a passing
flying saucer and expain that it's vitally important you get away before your phone
bill arrives.
By the way, the series was first only a trilogy, and although there are now six books, it is still called the Hitchhiker's Trilogy by devout followers
The Six Books of "The Hitchhiker's Guide to the Galaxy" Trilogy
The Hitchhiker's Guide to the Galaxy
The Restaurant at the End of the Universe
Life, the Universe and Everything
So Long, and Thanks for All the Fish
Young Zaphod Plays It Safe*
Mostly Harmless
* "Young Zaphod Plays It Safe" is very short but very important. It tries not to explain who Arthur Dent really is.
Cheers!