What would you do?

I would stun the bastard.

What would you do if you were being hunted by death eaters?

Run.

all of us are first years, we can't apparate until 6th year. We also don't know stunning spells (at least I don't yet)

What would you do if you someone threw you into the ocean?

I'd try to find something that floats and see if there was a ship nearby.
What would you do if you got your foot caught in a mousetrap? (yikes)

Um, go to the hospital wing, and later ask the caretaker not to place mouse traps where students are walking.

What would you do if your favorite author died (sorry for the bleakness).

He already did...

What would you do if suddenly a friend refused to communicate with you - not in speaking or in writing, and even pretended not seeing you when you two passed each other?

I would try to get over them

What would you do if your family suddenly kicks you out?

I would shout at them, "ITS NOT MY FAULT I GOT GRYFFINDOR INSTEAD OF SLYTHERIN!"

What would you do if you were sucked into space

Look for aliens.

What would you do if you found a muggle who could do magic?

I would immediately ask how she knew, obliviate her, (once I learn how <ouo>) and take her to the minister

What would you do if you were smaller than everyone else?

I would wear heels, they look good, so why not.

What would you do if you were taller than everyone else?