Ooo, but I already have seen one. I was looking out of my window and saw a long-black haired thingie with white clothing. As a Muslim, I would read the Quran, but lets not go through that, as this is not a religious thread.
I would take a picture, obviously. And second I would engage in good conversation. You never know what interesting conversations you could be having with a ghost.
I've always thought about this. Similar situation: Do any of you ever check behind the shower curtain late at night to see if anything/anyone is in there? I've done this many times without thinking, "WHAT IN THE WORLD WOULD I DO IF THERE WAS SOMEONE IN THERE?" I mean really, if it was a person I'd scream, but probably be screwed considering anyone sneaking into and hiding in your house can't have good intentions. If it was a ghost or something else supernatural what could I do? Scream? I probably would be to scared to do that or even move at all. I'd probably be stuck with ****ing my pants. There's nothing you really can do. No good options except hope it doesn't happen to you.
Would it be a friendly ghost? I would talk to the nice friendly ghost. If it was a mean ghost I would run away and move. Why do I need these things in my life?