How did Switzerland avoid getting dragged into World War II along with the rest of Europe?

Switzerland prided itself on its neutrality in world
affairs at that time(and still does).  It also did not participate in World War I or any
other wars for centuries prior, so there was a longstanding tradition of neutrality that
the Swiss wished very deeply to maintain.

A second reason
is geography.  Switzerland is surrounded by the Alps mountain range, with limited passes
and access points for armor and infantry to invade.  This makes it both discouraging for
attacking armies and easy to defend.  Hitler's air force, the Luftwaffe, was engaged in
small skirmishes with the Swiss Air Force (who, ironically, had bought German Me-109's
for their defense) but Hitler was never that interested in actually invading the
country.  The one time he brought it up, his generals quickly talked him out of it.  He
also did not feel the least bit threatened by them.

Lastly,
Switzerland was no pushover militarily.  They maintained a large standing army and were
reasonably well equipped, in the belief that the best way to avoid war was through a
strong defensive  force (armed neutrality) that would make an invasion too costly to
attempt.