Asking questions in French - formal and informal

Hi there
I am getting really muddled up with asking questions in French. There seem to be many different ways to ask questions. Can anyone please help with the simplest way first and then explain why and when I would change to a different format. 
thank you 

The inversion form is the most formal, and  something we don't use in conversation unless it's a debate. It's pretty much just used for written essays or philosophical text. If you're writing to a friend or even a supervisor, you wouldn't use this form.

The standard conversation form would be « Qu'est-ce que... », « Est-ce que... »  or the "question word + verb" form. This is polite enough to use with a stranger, but also not so overly formal that a person you tutoie would look at you funny.

The "question word at the end" form, is the most informal and casual, and something you would use for family or close friends. I wouldn't use it on a stranger. (For example, I wouldn't say « Vous faites quoi ? » to ask a stranger what he does for a living, but to my cousins...sure.)

Yes and the easiest, the inversion form, you just raise your voice at the end of a declarative statement, for instance; "it's a nice day?"

"Qu'est-ce que" seems to be used all the time for "what"; "Qu'est-ce que tu fais?"(What are you doing?)  You will get the hang of it soon.

Thank you for the info. That clears it up a bit more for me. Esp what to use for "what"!
I will keep at it.  

Lesson 2.7 in Module 2, Premium Level 1 explains the difference between y a-t-il... and est-ce que... to ask a question, the former where there is a noun and the latter where there is a verb.  But this particular example seems to take either/or form.  Is that right?  Would one or other form of the question sound better?  Thank you.  

In my experience, «Est-ce qu'il y a...» is more common for asking the presence (or absence) of something in spoken French, and also for "casual" written French.

«Y-a-t-il...» is something I see more on a professional, written context.

Okay, thanks for that tip torusan.