Step1
Pick a "question word" that indicates what specific kind of answer you're looking for. For example who, what, where ...
QUESTION WORDS
Combien = how many
Comment = how
Pourquoi = why
Ou = where
Quand = when
Que = what (Que + est-ce que --> qu'est-ce que)
Qui = who
Quel/quelle/quels/quelles = which of something (eg. Quelle table
= which table)
Step2
Indicate you are asking a question (and not just stating a sentence) by doing one of three things.
1) Use the TONE of your voice. This is, by far, the easiest method and requires the least thought in a face to face situation. If you go with this option, you don't need a question word because you're basically just stating a normal sentence as though it had a question mark at the end. However, these kinds of questions are often limited to "yes" and "no" answers.
ex. He likes dogs?/Il aime les chiens?
2) Use INVERSION. This means switching the order of the subject and the verb to change something from a statement to a question. This technique is useful when it is necessary to convert an already presented French sentence into question form. If you use inversion with a subject pronoun put in a hyphen (and a "t" too if the verb, such as va, ends with a vowel and the pronoun, such as il or elle, starts with a vowel).
Ex. Comment etes-vous? (How are you?) Comment va-t-elle? (how is she?)
3) The third option is a little more challenging. To use it, you must figure out whether the answer you're looking for is doing an action or having one done to it. In grammatical terms, is it the subject or the object? Once you have this figured out, you can insert either EST-CE QUE (object) or EST-CE QUI (subject) after the question word to indicate that you are asking a question.
These can be tricky to use. One clue is that "est-ce qui" is usually only used when dealing with the question words "que" (what) and "qui" (who). So, if you have already noted that you are using a question word other than these such as "comment"(how), then you are pretty safe using "est-ce que."
One more thing to note is that plain "Qui" can also stand in for the entire expression "Qui est-ce qui" which is a very formal way of speaking. So if your question word is "qui" and your indicator expression is "est-ce qui" you can cross both out and put "Qui" in where they were. Either option is fine.
ex. Qui est-ce qui mange le diner? (Who is eating dinner?)
*Notice in this example the person is doing the action (eating) so "est-ce qui" is used.
ex. Qui est-ce que tu aimes? (Who do you like?)
*Notice that the person whom you are asking about is being liked/having the action done to him or her, so "est-ce que" is used.