Kotor itself is a small town, so pretty much everything is within walking distance. Enter the old town via any of the three gates then explore the maze of narrow passages between the stone houses.
Parking space in the city center is very hard to find, so use your car only when you have to. Be careful where you park, sketchy tow operators target tourists around the old city.
There are no sandy beaches in Kotor, and water is not of premium quality for swimming. The best solution is driving to the Jaz or Trsteno beaches on the Budva riviera, some 20 km from Kotor. Those are very beautiful beaches, and you should make the effort of going there.
