Numerous hitch-hickers around the Galaxy know that the best way to
understand a foreign language is, by far, a Babelfish. Nevertheless, these useful devices
are known to be quite difficult to find on Earth.¹

This implies that, besides getting a translator to work for you, the best
alternative is starting to learn a new language. It isn't only useful,
it can be very interesting and, simply, fun!

Language Courses

There are many ways to try and learn a language, and none of them can
be said to be the best; everybody can find one or the other to be the
most suitable.

Due to proper advertising, taking a language course
looks the most obvious to many people. Sadly, this is not always true:
Six years of learning English at school had brought me to a stage at which,
despite being able to read and write it in a fairly acceptable way
(mostly because of my interests in computers and telecommunication), I
was completely unable to speak it properly, or understand a sentence
uttered at a normal speed with a foreign accent. (That is, foreign to
an Italian, like myself.)

I have seen much better results with other people, but none of them
were Italian. This is why I wouldn't disregard language courses
completely, but simply believe that the ones taught in Italian schools
sport some peculiar features in the area of uselessness.

Full or Partial Immersion

I acknowledge (but not necessarily endorse) that some fathers teach
their children to swim by bringing them rather off
the coast, and dropping them into the water. (I have first-hand
information that this sometimes applies also to humans.) This method
seems to work reasonably well in languages, too. The procedure is
simple: You reach a country or place where the language of your
interest is spoken, and interact with people until you reach the
desired degree of fluency in communication.

There is a variation on this theme that can be employed in any
setting in which you could apply the above-mentioned method, but for
any reasons you speak your native language during the day (e.g. at
your workplace). At night, you drop by one (or more) of the local
alcoholic entertainment establishments, no matter what they are named,
and you get drunk with the indigenous population. It might not grant
you a very fast advance in your language skills, but you will become
soon proficient in the dictionary area embracing drinks,
the tools designed to contain them (bottles, glasses, etc.), and -
often - financial transactions, or you will be unable to continue
doing it. Besides, people seem to find it quite
enjoyable.²

Self-teaching

Another method should allow you to learn a language in a very
effective and noticeably inexpensive way, but I have not tried it out
on my own, so I cannot relate any direct experience in this regard.

It is said to have been suggested by the late linguist Mario
Lucidi. It can be used by whoever has a basic understanding of a
language's grammar and knows some hundreds of words, a level reachable
through any elementary course, but wonders how to learn more words.
Stated in a different way, it applies to those who try to read
something, but find out they have to look up almost every word on the
dictionary (often the same words again and again), and wonder why they
don't learn them.

You only need a book, a notebook and a dictionary. This is the
procedure that Lucidi explained:³

• Pick a book in your chosen language. It must be interesting to
  you for some reason: it may be by your favourite writer, or you may
  need it on your job, for example.
• Decide how long you want to study every day. If you need an
  hour to read a page, then it may be an hour, for instance.
• On the first day read page 1, looking up on your dictionary
  every word you do not understand, until you understand each sentence's
  meaning perfectly. Remember, though, to underline each such word with
  a pencil.
• On the second day, copy every word you underlined on page 1 onto
  your notebook, on a column. While you are writing them, look up every
  word whose meaning you have forgotten. Then, read page 2 and
  underline every word you have to look up.
• On the third day, write on your notebook the translation of
  every word you copied on day 2, and obviously look up every word whose
  meaning you have forgotten. Then, you write on a column the words you
  underlined on day 2, and look up those you have forgotten. Then, read
  page 3, always looking up and underlining every word you do not
  understand.
• On the fourth day, use a piece of cardboard to cover the
  translation of the words on page 1 and you check, word by word, if you
  remember each of them. If you can't remember one, you slide down
  your piece of cardboard and read the translation. Then, write the
  translation of the foreign words on page 2 (which you wrote on day 3),
  and write the foreign words you found on page 3. In both cases, you
  must look up the words you don't remember. Finally, read page 4 and
  underline the words you have to look up.
• On the fifth day glance at the list of the words you found on
  page 1... they should look rather familiar by now. Cover the
  translation of the words on page 2, and check (always one by one) if
  you remember them. Write down the translations of the words on page
  3, and the very words you underlined on page 4. Now you can read page
  5, and underline the words you have to look up.

The description may sound boring, but the average drinking games is equally iterative, yet people deem it funny: It might be worth trying. Moreover, as days pass you
should become faster and faster, since you are increasingly acquainted
with the procedure, and you know more and more words; managing to read
two, three or more pages in the time you used to spend for just one
page should be a remarkable reward.