You can improve your language and style by using various grammatical structures, e.g. structures that help you to create complex sentences instead of simple sentences. Here are a few tips.

• conjunctions: a) coordinating (for, and, nor, but, or, yet, and so); b) correlative (both … and, [n]either … [n]or, and not [only] … but [also], whether … or); c) subordinating (after, although, as much as, as long as, as soon as, because, before, if, in order that, lest, since, so that, than, that, though, unless, until, when, whenever, where, wherever, whether, and while)
• relative clauses to connect sentences and/or add extra information (who/whose/whom, which, that)
• participle clauses (e.g.: When she reads a book Reading a book, she forgets everything around her.)
• gerunds (e.g.: He remembers how his mother cooked his favourite dishes his mother cooking his favourite dishes.)
• if-clauses (e.g.: If she had known, she could have helped.)

• tenses: Make sure you know when to use a) Past perfect, Present perfect, Past tense, Present tense, Future tense; b) Simple form (She reads the newspaper.) or Progressive/continuous form (She is reading the newspaper.)
• referencing: a) congruency, i.e.: Do verb and/or personal pronouns match the subject in number and person (singular/plural, 3rd-person ending in simple present)?; b) use of personal pronouns, i.e.: Did you clearly mention the subject or object you are referring to with a personal pronoun? (Before you can write about him, you need to state who that him is.)
• grammatical patterns: Depending on the vocabulary you use, certain grammatical structures will be inevitable, e.g.: Some verbs require a direct object instead of a prepositional object. (They were discussing about the topic.)
• active/passive voice: Make sure that you stick to standard English! Passive voice consists of the verb to be + past participle. (In informal, spoken American English, you will often hear a version that includes the verb to get.) Thus, the correct sentence reads: She got was bullied by the boy next door.
• adverb vs. adjective
• word order, especially position and order of adverbs: Check http://grammar.ccc.commnet.edu/grammar/adverbs.htm.

• linking phrases/connectors to structure your text and to link paragraphs/sentences (e.g.: First, / Second, … etc.; Furthermore, … / Moreover, …; → Check this pdf-document: Flinders University help sheet.
• paragraphing: Paragraphs show the reader that you (= the author) are starting a new topic or thought, and that both your ideas and your writing are developing and moving towards the next step. This should be reflected in your use of paragraphs. Some information and exercises can be found here: BBC: Paragraphing and BBC: Structure and Paragraphs.

If you are having difficulties with punctuation, hyphenation, etc., these style sheets may help:

• University of Oxford: Writing and Style Guide
• MLA Style Sheet(long version) (The Modern Language Association (MLA), New York, has published the so-called MLA Handbook which helps you with how to do research and cite properly. The guidelines describe rules of formatting text, incl. spacing, citation, punctuation, etc.)