This part of the game doesn't involve much fighting. Once in Windemire, simply talk to everyone. You can go complete the quest in this place right away but I recommend fighting around and buying a Clawsword. (You'll need it for the next area!) Once you have the Clawsword go to the shop and buy a bomb. Head to the screen with the duck idol statue on it. You'll notice that there is a ring of stones surrounding the duck idol and you can't get in - or so it seems. On the north part of the screen you should notice a rock that is somewhat black and has some cracks in it. Place your bomb there and blow up the rock. You're now allowed access to the area around the duck idol. Grab the treasure and then slaughter EVERY duck. Once this is done a short automatic sequence will happen and the people here will no longer praise the ducks.
You could leave this place right away but there is some stuff you can do. First, explore the country side and pick up any items you find. There is a secret area here and if you wish to know where it is consult the secrets section of the page. (Under Info:Secrets) Second, you can go to the mayor's house and follow the underground passage to an island. Enter the first house you see and you'll find out a girl is missing. Another short automatic sequence will occur and in the end you'll have to fight two dragons. Dispose of them quickly with the Clawsword you bought. Now the guy offers you throwing axes to buy. You might want to buy them to kill the monsters around Windemere quickly and from a distance for gold and experience. You'll need the extra gold and experience for the next area. Now head back to Goodheart castle and you'll be allowed entrance. Inside, you'll ask if you can go find Milder and the king will grant you permission and open a path to the north. Go north of the castle till you hit the cliffs and follow the path east along the edge of the cliffs. You'll soon reach a cave that leads to the next area.