Keep in mind, using the Wetlands Mapper and/or the Web Soil Survey is NOT the same thing as hiring a wetlands consultant and/or having the USACE do a delineation on your property (so realize, there are no guarantees with this approach). However, if you're just looking for an educated guess, both of these online tools can be used as a starting point.
Selling land is one of the most difficult real estate transactions to conclude. The seller must create an imaginary future for that land and market it to the appropriate buyers. This involves creative thinking on the part of the owner and the expense of illustrating the future use of the land in the form of flyers and brochures. Obtaining financing is difficult and requires the owner to be flexible on his price and terms if he wants to sell the land quickly.
After identifying your likely buyers, try to think like them so you can focus your message to convey what they need to know about your property. Have information ready about schools, shopping and other nearby amenities. For developable land you can be prepared with zoning information and insight from local authorities about the location and capacity of water and sewer service. Each property is different, so customize your information for your situation and your targeted buyers.