Here's how I like it..

1 1/2 Cups Milk
1 Cup Water
1 Cup Oats
3-4 Tablespoons Sugar
1 Teaspoon Vanilla Extract

Bring water and 1 cup of milk to the boil. Reduce to simmer and add the oats, sugar and vanilla. Simmer gently for 3-4 mins. Add 1/2 cup of milk and leave to stand for 2-3 mins.