Scotty, dead and dying elms are the most reliable trees to hunt around in Indiana. Elms prefer VERY moist soil, so they tend to grow in valleys and creek beds, but try to avoid areas that flood regularly. Creek beds that have a fairly steep grade and receive runoff from surrounding hills are a good place to start. Once u get good at identifying the others (poplar and ash), u can increase ur search area to include southern facing slopes that have these trees. As far as soil goes, u want a good sandy loam. That is, dark moist soil that u can form a ball with in ur hand but crumbles apart easily. This soil is ideal as it allows for maximum moisture absorbancy without turning
into sloppy mud. Stay away from hard red clay, its hard for mush to push thru. Learn ur trees, and stick to good soil, and you'll have success.