increasing vocabulary

CULTIVATE AN INTEREST IN WORDS. -and a very good reading habit. care must be taken to see that you read good authors using standard English . eg.., books of P.G.Wodehouse. while reading,try and remember the words , their meanings in context, . read some interesting books on word origins-- and association of ideas would also help you remember the words and meanings. you get a good Command over the language with the passage of time , and when you make a very conscious effort. There is no substitute to reading. you can do some exercises in "synthesis of sentences" trying to master combinations of sentences. incidentally, your 'weather' must be 'whether' and you must say 'enrich' your vocabulary. 'improve' is also better than 'increase' in this context.Regarding these entrance tests learning roots and origins of words will help a bit.

Reading books, newsletter. Things about politc and more. My english vocabulary isn't big. But my portuguese is good!

I'm sorry but you just used the word 'weather' incorrectly up there. You should have used 'whether', that's the appropriate word. They're homophones and if you type real fast, sometimes you really don't realize you misspelled or typed the wrong word. Anyway, for your question, I always read books or articles from newspapes and always keep a dictionary beside to check words that are new to me. I also sometimes just browse through the dictionary and check for words that are new to me.