A common strategy for starting games is to randomly click until you get a big opening with lots of numbers. If you flag all of the mines touching a number, chording on the number opens the remaining squares. Chording is when you press both mouse buttons at the same time. This can save you a lot of work!
With your cursor inside the minesweeper window type "XYZZY" then press Shift-Enter and Enter. A white dot should appear in the upper-left corner of the screen. If it turns black, your cursor is resting on a mine.
It was believed that on that day, the souls of the dead returned to their homes, so people dressed in costumes and lit bonfires to ward off spirits. In this way, popular Halloween tropes such as witches, ghosts, and goblins became associated with the holiday.