Luke 6: 38 is a beautiful illustration of God's willingness to give to His children. But you may miss the nuances if you're not familiar with open market commerce.The majority of the world does not buy their groceries from Grocery stores, but rather open, outdoor markets where people bring their goods to a central gathering place to buy, sell, barter, and trade.
One merchant may be selling out of a large 100# bag of flour; another out of a bag of sugar; ;yet another out of rice. The seller uses a measuring containter (many times an old metal can or jar) to maintain consistency of the amount sold. The measure could be as small as a little mushroom can or as large as a gallon fruit can.
This measure used to sell goods in the marketplace is what Jesus is speaking of here in Luke 6. Your choice of measure to give to others will be taken and used to measure back to you God's gifts.
A "good measure" would imply using a large container rather than a small one. "Pressing" that measure down would imply maxing out the amount of space available. This is common when selling sugar. "Shaken together" would also be a way of using all the area in the container. Shaking rice down would allow more to be put in the can. "Running over" happens when the merchant continues to pour the goods on again and again until the product actually forms a peak and the container cannot hold one more speck. "Poured into your lap" actually happens when a woman is wearing an apron and uses it as her bag.
