Re: What is the best episode to introduce a person to Trek to?
I'd go with The Survivors, as it's not only great but pretty self contained.
Q-Who is the best, but I'm guessing you don't want to be explaining who Q is and so forth
No, Q-Who would be a great choice. I was just thinking about that one. It's the kind of episode that doesn't rely on a lot of backstory other than explaining that Q is an omnipotent being that occasionally shows up and causes mischief. It introduces vibrant characters like Q and Guinan to the first time watcher as well as the Federation's most intimidating enemy. It's got everything. It's the kind of episode that might have your friend asking you stuff during the episode which would be a good thing if it meant his/her interest was piked.
Searching for something, a million miles and a ways to go.