A tip for when you have cooked something like a lamb casserole, and you want to serve it straight away. To remove the layer of fat that floats at the top just chuck in a few ice cubes. The fat goes cold and immediately sticks to the ice cubes. Scoop out with a slottted spoon and throw away, then just bring your casserole/gravy or whatever back up to heat. Of course you could always leave it overnight in the fridge and take off the fat that way.