The passive voice should not be used. Use the active voice. Find ways to rephrase such constructions. Edit your work. Dashes can be useful sometimes, but they can usually be replaced with commas, colons, semicolons, or periods to improve clarity.
Sentence fragments a no-no.
Write in complete sentences. And starting sentences with conjunctions is bad, too. Although this technique can be useful at times, it often takes the place of a thoughtful transition by offering an easy out. Resist the temptation. Writing carefully, dangling participles should be avoided.