I am using a 12 gage tomorrow to go deer and squirl hunting. I plan on sitting in my stand with friends in the morning for deer and then around 11 shooting some squirls. This will keep me from having to bring two guns.I have never killed a deer with slugs. What do I need to know?

About how far can I shoot?
What do I need to look for when buyiing slugs in a few mins?
What shot, weight etc?
Do I need to aim a little high or what?

What am I forgetting?