This study aims to suggest basic post-editing guidelines for Korean-English machine translation of informative texts. After constructing a parallel corpus composed of sentences extracted from an actual MTPE project, a qualitative analysis was conducted to find out which items were post-edited and how they were revised while Korean source texts went through machine translation, post-editing by translators, and revision by editors. The study categorized post-edited items into seven broad categories of format, typo, lexis, grammar, structure, addition, and ommission, classified them into thirty-five sub-categories, and counted the number of items under each sub-category. The result shows that the post-edited items vary from typos and grammatical errors to structural changes and omission of elements. The study also found that post-editors in the project, both translators and editors, post-edited not only errors but also non-errors. Lastly, this study suggests post-editing guidelines based on its findings, which can serve as guidelines for actual MTPE projects to improve post-edited outputs as well as a practical guide for those who want to learn post-editing in action.