Skim Fat from Whole Milk

If only whole milk is available, and that's not what you want, you can try to skim the milk yourself.

Steps

Check the label on the jug or bottle to see whether the milk has been homogenized or not. If it's homogenized, you're out of luck.
If the milk has not been homogenized, let the container sit quietly for several hours with the lid or some sort of cover on top. Milk is actually a liquid with bits of solid particles floating around, so if you let it sit for a while, the particles will soon "settle".
Open the container. You should see a layer of cream floating on top of it.
Scoop the cream off the top with the spoon to lower the milk's fat content. Do this gently and carefully, if you shake the container the fat will be redistributed in the milk and you may have to start all over again.
Repeat, if desired, until the desired amount of cream has been removed.

If you have enough cream, you can shake or whip it, and it will eventually turn into unsalted butter.
If the milk is in a container with a very small opening, (e.g., a plastic milk jug), you may want to transfer it to a container with a larger opening, so that you can get a spoon to the top of the milk easily.
Most milk sold in the United States is homogenized, which means it has been processed so that the fat globs are broken up very finely and distributed evenly through the milk. Homogenized milk will never settle with the cream on the top.

If you let the milk sit around too long, the solid particles will clump together and create a yogurt-like substance. Not what you wanted at all!