First of all you should be clear about what to write and make an outline for your writing before starting. Your aim must be writing a well-organized one . So you should write introduction paragraph firstly and in developing part you should support whay you said in introduction through examples and conclusion part will be short and concise.You'd better use conjuctions such as First of all , On the one hand , However, Furthermore etc , adverbs , interesting vocabulary to enrich your writing. Even quotoes you can use in your writing. It shouldn't be too long or too short.As you practice writing, you'll get better.