Rule No. 1 : Never visit a country with less than a week in hand.
Rule No. 2 : If arrival and departure are from the same city, plan the sightseeing in that city for the last 1 or 2 days. Makes it easier to stay near before you leave, lesser chances of missing the flight due to any hold-up.
Rule No. 3 : Tour packages are a strict No-No. There is no greater adventure than exploring a new place on your own.