Enjoy the beaches, with adequate amount of beach gear including sunscreens, hats, sunglasses, loose comfortable cotton clothes, carry bags, plenty of water.
If you plan to drive into Goa¸ then do remember that the rounds are steep and winding. Carry tablets or lime to avoid motion sickness.
The sea is rough during the monsoon season. Don't get caught in the sea at that time.
When visiting forts and monuments look for kids who show you sites with their binoculars. It is a cheap and easy way to discover the place.