The main ingredient for a person cooking meth in your part of the country is anhydrous ammonia. I'm sure, just like Indiana, there is a lot of it around at farms and co-ops. A propane tank is the most common way to transport it and may have a different fitting on it then normal. Green around the brass fitting is an indication of anhydrous. Some other items you might find are bubble packs for cold medicine, anything with a high concentration of iodine, the coffee filters, packs of ephidren tablets, and obviously any over the counter chemical container. Butane is also a precursor that is commonly found.
I could smell every lab I ever came across before I could see it. It is usually hidden good and close to a road or water. The road is because they are too damn lazy to walk far, and the water is in case they get anhydrous all over them. If you smell a strong chemical odor you may be near one.