Twitter is a great place to improve your reading and vocabulary skills. There are many accounts you can follow to learn new vocabulary or phrases each day. Here are just a few examples: @bbcle, @RolloffTongue, @MacDictionary, and @VocabularyNinja.
To improve your grammar, follow accounts like @Grammarly, @EnglishClub, @GrammarMonkeys, @The_YUNiversity, @English247, @GrammarGirl to discover quizzes, exercises, images and tips. Use the hashtag #grammar to discover more free grammar resources.
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Twitter Tutorial for Beginners (YouTube)