At the kitchen, I washed the stems+ leaves with tap water, and washed my hands...very important for cooks to do this steps particularly when dealing with food that will be eaten fresh or stored raw/non-cook.
Next, separate the leaves from the stems a place them on a separate bowl or directly on a blender. Also mince one garlic (terminology?) and get the olive oil and the cup measure ready. I
I use 2 1/2 cups of olive oil. I add the first cup and about 1/3 of the leaves and press grind. Now add the garlic and grind. Mix.
Add the other 1 1/2 cup of olive oil and the leaves in small increment. At this time the blender will begin to protest and you need to help a little stirring the mix from top with the help of a wooden spoon. Continue the process until you grind all the leaves. This is really the basic pesto. This recipe yields a 300-400 g of plain pesto.
If you want to keep the pesto for a long period of time, you need to add some kind of preservatives. I prefer spices such as pepper and salt.
You can experiment with pesto flavors. The most common additives for enhanced flavors include sea salt, aged Mozzarella cheese, hot peppers, and pine nuts.