One of the most useful language tools is a dictionary.  These days it may seem fashionable to use an electronic dictionary and translation device, but there is no substitute for a good, monolingual, English dictionary.  You will find it useful for both writing and reading.  Besides, (as any one who has had a conversation or read the writing of someone who uses an electronic dictionary will tell you) the electronic dictionary and translator can often make your writing worse and communication more difficult because the translation is not written by a native speaker.  A translation dictionary should never be used in conversation and only be used in writing when you have no idea what the word is.  Even after looking up a word in a translation dictionary, you should still make sure it is the word you want by checking it in an English dictionary.  If you don't believe me, try copying the text of this article and pasting it into a translation website like Babel fish.  Translate it back to your language and see how readable it is.  
 
The other advantage to an English dictionary is it will give you more practice in understanding English.  To become fluent in any language, one must learn to think in that language.  By using a translation dictionary your brain is forced to go back and forth between your native language and English.  This is necessary for the beginner, but it can slow learning at intermediate and higher levels.  When using and studying English, keep yourself thinking and analyzing in English as much as possible, too.  As a former teacher once told me, "The day you dream in another language is the day you can truly start thinking of yourself as fluent".   An additional benefit of using an English dictionary is that you can immediately see how a word is used. A good dictionary often provides example sentences.
 
The most important thing is to get a good dictionary.  There are several choices, but I recommend buying a "learners dictionary" such as The Oxford Advanced Learner's Dictionary or The Longman Active Study Dictionary.  Spend some time in the bookstore browsing through the various choices.  You should look through several dictionaries, checking to make sure that the definitions are written in ways that are easy for you to understand.  The Oxford English Dictionary may look impressive, but it is useless to you if the definition is more confusing than the word itself.  Choose a few words you already know and look them up.  Is the definition what you expected?  Next, choose a few words you are less sure of.  Did the definition make the word clearer in your mind?  Finally look at the example sentences the dictionary provides.  Are these examples clear to you?  If you answer "yes" to these questions, you have most likely found the dictionary for you.
 
Finally, you must make sure you know how to effectively use your dictionary.  Read the first few pages of your dictionary as they will give you excellent instructions on how to use it, and the symbols and abbreviations it uses.  A good dictionary will also have a phonetic table that tells you how to pronounce the phonetic symbols of words.  Also, it can teach about stress marks of words so you have the correct intonation.  In this way it can also be a useful tool for pronunciation.  Make sure to check the correct usage of the word; is it a noun, verb, adjective or adverb?  If the word has more than one meaning, check the example sentences to see how it is used differently for different meanings.  Most dictionaries will have the most common definition listed first.  Make sure to check if it is in common usage and whether it is a formal or informal word. 

 

With more practice using your dictionary will become easier to use and it will become an essential tool in your English studies.  So, set aside that translation dictionary and start having fun using your English dictionary.  You may find it to be quite illuminating.