Butter is incredibly easy to make. We enjoy making butter as a family. I churn butter in a commercial blender, while my children shake jars of cream. In three minutes butter floats on top of buttermilk. 
You will need:
1 quart of cream (cold works best) blender or a mixer
colander
cold water
salt
Skim cream from milk with a ladle. Generally, it works best to let the milk sit for 24 hours in the refrigerator to allow the cream to rise fully. Place cream in a blender or use a mixer. It is important to keep the speed low. Churning the butter on high speeds heats up the butterfat and gives poor results. The cream may not churn into butter or it may be weak and pastey. The cream will get turned into thick whipping cream before it becomes butter. Keep churning, you almost have butter. Once the butter is floating on top of the buttermilk, you can drain off the buttermilk.
Buttermilk is excellent for cooking. Fresh buttermilk will have little flavor. After a few days acidity will build up and it will sour. If buttermilk becomes to sour, dilute it with milk.
Place the butter in a bowl and rinse it with cold water. While rinsing the butter, mash and knead it. Pour off the water frequently. Continue rinsing the butter until the water is clear. The key to good butter is rinsing out all the buttermilk. Salt the butter to taste. Place it in a crock. We often freeze butter until we need it. We keep butter in the refrigerator, but we have heard of many keeping it at room temperature, consuming it quickly with no rancid flavor developing.
*Butter can be made from soured cream. In fact, French treasure sour cream butter. Sour cream butter does have a more robust flavor. France chides Americans because we do not have real butter.
*Add kefir to the cream and allow it to sit out on the counter until thick. The resulting product is cultured butter, filled with healthy enzymes.
*Butter can also be made from thick cream. Thick cream is mechanically separated. Thick cream can be hard on motors of blenders. Dilute the heavy cream with equal amounts of milk.