If your first language has no articles, English articles are not a small detail you can pick up later. They are a decision you are forced to make in front of almost every noun you write, and getting them wrong is the single most visible marker of non-native writing. The words are tiny. The signal they send is not.
What follows is the pattern behind the mistakes, rather than a list to memorise.
Articles are not decoration, they are information
An article tells the reader whether a noun is one of many, a specific one you both already know about, or a general idea. That is genuine information, which is why English refuses to let you skip it.
Wrong: She is teacher. Right: She is a teacher.
"Teacher" is a countable noun, and a singular countable noun cannot stand alone. It needs an article or another determiner. There is no version of this sentence where the bare noun is acceptable, which is what makes the omission so noticeable.
The most common cause is transfer, not carelessness
Wrong: I bought car yesterday. Right: I bought a car yesterday.
Writers whose first language marks definiteness through word order, case, or context rather than through articles tend to omit a, an and the wholesale. This is not sloppiness. The category simply does not exist in the source language, so there is nothing to translate. Recognising that it is systematic is useful, because it means the fix is systematic too: check every singular countable noun, every time, until it stops requiring thought.
Use "the" when the thing is already identified
Wrong: Sun is bright today. Right: The sun is bright today.
"The" says: you already know which one I mean. There is only one sun, so it is identified before you finish the sentence. The same applies to anything you have already mentioned, or that context makes unambiguous.
But do not use "the" for general statements
Wrong: The dogs are loyal animals. Right: Dogs are loyal animals.
Wrong: The honesty is best policy. Right: Honesty is the best policy.
This is the mirror-image error, and writers who have learned to add articles often overcorrect into it. General statements about plural countable nouns take no article, and most abstract uncountable nouns used generally take none either. "The dogs" means some particular dogs that we both have in mind, not dogs as a category.
"A" and "an" follow sound, not spelling
Wrong: He is a honest man. Right: He is an honest man.
The rule is about the vowel SOUND that begins the word, not the letter. "Honest" starts with a silent h, so it begins with a vowel sound and takes "an". The same logic runs the other way: a university, a one-way street. Both start with consonant sounds despite their spelling.
The practical order to check in
When you reread a sentence, ask three questions in this order. Is the noun countable and singular? Then it needs an article or another determiner, always. Is it already identified for the reader? Then the article is "the". Is the statement general rather than about specific instances? Then a plural or uncountable noun usually takes no article at all.
That sequence resolves most article errors without any memorisation, because it follows the actual logic rather than a list of exceptions.
If you want a second pass over your writing that catches this class of thing while you concentrate on what you are actually saying, the BeLikeNative writing assistant is built for exactly that.