Correctly written expressions deliver the intended message honestly. The word ‘correct’ comprises a wide range of concepts; like the use of appropriate words; grammatical structure and use, spelling rule, as well as the aptness of materials on which a language text is used, legibility of the text, color and font of the text, etc. The collective effort of all the above things, and also of other things, brings about the desired outcome, effective communication. If one or the other is missing the desired message intended to be conveyed could failed. This book is designed to minimize writing mistake in using the Oromo Writing System by identifying commonly committed errors and their possible causative factors. The mistakes are identified to be ranging from simple structural problems to complex semantic ambiguity and vagueness. As solution the writers need to take basic course on the Oromo writing system; besides guide to write the language need to be prepared. Moreover, all concerned bodies have to be responsible to improve, standardize, and establish consistent way of using the writing system of the language.