If you're going to Phillip Island you can see Koalas at the Koala conservation centre or Maru Koala Park in Grantville.  If you want to see koalas in a natural 'wild' environment then the conservation centre does that, but if you want to get really close to them then Maru is best for that.  At Maru the staff take you right inside the koala area and you can see them really close and they also do photos of you with the koalas.  Maru is a family run place and the staff are all very friendly and give talks about the koalas.  You can also hand feed and pat a lot of the animals like the kangaroos and wallabies.