Proper air drying is key to attaining high quality stock. The biggest principles of the process are: airflow, rain cover and spacing. After doing a bit of research I was confident I could do the job myself. 

The first and most important step in drying lumber is selecting a location. The ideal space is flat, can support weight, has good airflow and covered. My barn was a decent fit for this, though it didn't have any natural air flow. After selecting a space in the barn, I got to work on laying the foundation for the stack. It is important to elevate the wood at about 2' off the ground to get good airflow out of the base. The easiest way to support that much weight at that elevation is with cinder blocks. I didn't have any so I took a trip to an old, crumbling silo that advertised free blocks. After picking through the rubble I managed to get 18 blocks that were in good shape. I layed 12  blocks out on the concrete floor (3x4) all spaced approximately 2' apart. Next, I layed the foundational boards (called mudsil) which spanned the cinder blocks vertically. For these boards I selected some beat up 2x4's I had lying around. After the foundation was down, I got to work laying out the boards. I started with the 2" thick pieces spacing them ~1" apart. Between layers, I placed 1" thick flooring boards which acted as my "stickers". Sticker boards space the wood to create good airflow during the dry process. They are placed perpindicular to the lumber and directly over the cinder blocks/mudsils foundation. Proper "stickering" keeps all the pressure points at uniform intervals and provides adequate airflow between rows. This facilitates uniform drying across the boards, less warping, and faster drying times. After the 2" boards, I layered the 1" boards and squeezed in the 4x4's in the back.  I made sure to do a top layer of stickers and placed cinder blocks for weight on top. Because my lumber was not uniform (in width or length), the final couple rows were quite difficult to organize. A final step, would be to paint the ends of the boards with latex paint to prevent cracking, but I failed to do this because most of the ends were inaccessible after I built the stack. If I get cracks, I will deal with them during my future builds.

For the first 3 months of drying I cycled a large shop fan on and off to create some good airflow throughout the stack. It was not perfect, but it prevented mildew and facilitated adequate wicking. I have since turned off the fan and the pile will sit untouched until the wood is dry enough to use. Most woodworkers will tell you that drying times vary widely based on a myriad of factors. The biggest factor by far is board width, though species, airflow and climate all play a role. Experts recommend 1 year of airdrying per inch thickness. That means I won't be able to start working with my 4x4s for 4 years! I do plan to dry some boards at a local kiln before then, but airdrying for the a year (at least 3 months) is recommended anyway before going to a kiln. The reason is that air drying is gradual and allows slow board movement, which leads to less warping. After the first year, the lumber will lose most of it's moisture and at that point a kiln will not cause too much board movement in it's extraction of the last few drops.