Salem on Halloween

I'm in NH and my sister is coming to visit over Halloween weekend.

Supernatural was her favorite show, she watches all the ghost hunting shows, has a pack of tarot cards, etc., and she insists that she wants to experience Halloween in Salem at least once in her life. So I guess that means I now have to experience Salem on Halloween.

All I really know is that it's a zoo on Halloween, so I have a couple questions:

• Is the MBTA lot in Newburyport going to fill up? If so, is there an alternative you can recommend for parking?

• What attractions are worth seeing, are reservations required for whatever one(s) you'd recommend, and what might be the wait times?

• Is there a good spot to escape to get a breather from the crowd during the festivities?

• What percent of people are in low-effort costumes (like just a witch hat) vs. high-effort vs. no costume at all?