Mortar is inexpensive and readily available at any major home improvement store. Making your own mortar allows you to fine-tune the mixture in response to any of a number of factors that you might run into during construction. You can mix quick-set mortar, slow-set mortar or even mortar that can be squeezed through a mortar joint applicator. The only thing you need to know is the correct percentage of ingredients to use in making basic mortar, and then find the best mixture for your purposes by either adding or subtracting ingredients.
Dump four parts Portland cement into the wheelbarrow. You can use any container for measuring, because it isn't the actual amount that is important, but rather the percentage of the Portland cement to hydrated lime.
Dump one part hydrated lime into the wheelbarrow, and then mix the first two ingredients thoroughly with the garden hoe.
Add nine parts fine sand or other fine aggregate material to the mixture. The sand or aggregate can be play sand, though this type of sand is generally more expensive than cement sand. Use the garden hoe to thoroughly combine the mixture. This is the formula for basic mortar. To use, add water until the mixture is the consistency of peanut butter. This mortar has a compressive strength of 2,500 pounds-per-square-inch.
Create mortar that is more prone to self-healing by adding one additional part of hydrated lime to the mixture prior to adding water. Self-healing is accomplished when the mortar's hydrated lime comes into contact with carbon dioxide in rainwater. The hydrated lime expands, filling cracks in the mortar, and reverts to limestone. This is called autogenous healing. This reduces the mortar's compressive strength to 1,800 pounds-per-square-inch, but is still sufficient for use in most home applications.