Preferably all the time, it makes communication so much easier when your audience is general, rather than just a small group of friends. Especially when applying for jobs. And these three sentences are examples of poor grammar.
It's you are, you is is not proper grammar.
It's you are, you is is not proper grammar.
Use proper grammar!
very good grammar (proper grammar)
"She did not have" is the proper grammar.
Yes, but you sure didn't.
Use proper grammar.
Use proper grammar
if you want a proper answer use proper grammar
if you want a proper answer use proper grammar
How_do_you_get_the_dogs_on_mcworldAnd please use proper grammar.
Use proper grammar dude.