ESL students who wish to write well need help in understanding and avoiding mistakes in their writing. There are 4 main types of mistake in written language: spelling, punctuation, grammar and usage.
Spelling mistakes: English spelling is irregular and even many native-speaker adults have difficulties with it. Spelling mistakes do not usually prevent the reader from understanding what the writer is trying to say, but they can create a negative impression. For this reason it is advisable to try to remove them from important pieces of writing. Probably, the best way is to write on the computer and use a spellcheck. Diligent use of a dictionary is a good alternative. For high stakes writing, e.g. job applications, the piece should be given to a teacher to check over.
Extensive reading in English is a very good way in the longer term to learn English spelling patterns, so that mistakes are less likely.
Punctuation mistakes: ESL students need to learn certain aspects of the English punctuation system, such as the way to punctuate direct speech. In general, however, the most serious of punctuation mistakes are made not only by ESL students, but by native speakers too. These mistakes are due to the lack of a clear understanding of what a sentence is, and they result in fragments (incomplete sentences) or run-ons ('sentences' that do not end when they should).
Punctuation mistakes can often be spotted if the student reads the writing aloud. If a natural pause in the reading does not correspond with, say, a comma or a full-stop in the written text, then it is likely that the punctuation is faulty. Important writing should be given to a competent native-speaker to check.
Extensive reading, especially of non-fiction, both in English and the mother tongue, will help students understand the concept of the sentence as the basis of good writing.
Grammar mistakes are the next type of error commonly made by ESL students. For example, learners often do not choose the correct English verb tense for expressing an idea or do not use it in its correct form. They may fail to use the articles (a/the) correctly, or place words in the wrong order in a sentence.
Some grammar mistakes are easy for learners to correct themselves, particularly if they read their writing aloud. Other grammar mistakes are not easy to find, however, because the learner simply does not yet know the correct way to express an idea in English. Looking in a grammar book will not often help in such circumstances - the best thing to do is to ask a native speaker to check the writing.
In the long term most grammar mistakes will disappear by themselves, particularly if the learner does extensive reading in English.
Usage mistakes are the final type of error often seen in ESL students' writing. A usage mistake does not break a grammar "rule", but is a word or string of words that a native speaker would never use to express the particular meaning that the ESL student is trying to convey.
Usage mistakes can often be more of a problem to the reader than grammar mistakes. The ESL student who writes My mother don't speak English or Then I putted beaker on tripod will be understood. On the other hand, the student who writes in a journal My mother has an arrangement with her operator today will not be understood to mean that his mother has an appointment with her surgeon.
It is usage problems rather than grammar problems in extended pieces of writing that immediately identify even the most proficient of ESL students as non-native speakers. Once again, the short-term solution to usage problems is to ask a native speaker to check the work; and the long term solution is to do lots of reading in English.
Important: Learners should understand that the type of writing mistakes listed above are not the only problems to worry about in a piece of written work. In fact, there are aspects of writing that are much more important than the presence of small mistakes of spelling, grammar or usage. In order to get a good grade for a piece of written work, the student must be able to answer the following questions with Yes!:
[The above questions apply to a piece of expository writing, such as in history or science. Not all of them are applicable to creative pieces of writing in English class.]
The pages on this website outlining the writing process give detailed advice in how to become a better writer. This advice should be followed by all students, not just ESL learners, who want to write well.