Hi, everyone!

   It is doubtless that one of the most essential -and most given- tips, is practicing.
   Try always to spend some hours daily (or weekly, if you don't have lots of time) to do homework, look up words in the dictionary,  do extra work on your textbooks, talk with your teacher if you have any doubts, and many other small actions you can take repeatedly to make tiny but constant progress.
   Also, (even if your not self-taught), you can look up hepful sources where you can find practices, readings, audios or videos, or maybe find a forum, so you can practice with a partner and other English learners.
   So, for this, I will share you some common resources which can help you when you have time to dedicate to the language:

http://www.rd.com/
Reader's digest: Here you can find lots of readings, with the option to sort them by topic, and even by lenght (they have 100-word stories for English learners).

http://learningenglish.voanews.com/

Voice of America, Learning English: This is a platform made especially for non-nantive speakers. They have a variety of videos and audios (usually with their transcripts), based on recent news.

http://www.ticotimes.net/

The Tico Times News: For Costa Rican students (more advanced), this site provides also recent news about Costa Rica's reality.

And well, these are only a few, but there's enough time to search on the Internet for endless websites dedicated to English learners.
I hope you can find this useful, and broaden your options for this learning process.

Greetings to you all,
-Daniela