We need fresh and younger pilots in the ag industry. The average ag pilot age is climbing rapidly and it is increasingly difficult to get new talent trained and insurable.
The first step is to get as much tailwheel time as possible. Heavier and faster aircraft make for more desirable time, but even cub and champ time is good. 1000 hours of tailwheel time is a good starting point. In those hours it would be wise to go ahead and get an instrument rating and a commercial ticket.
The second step is to make contact with some local operators. Go by and hang out a bit. See if the job is really what you think it is. A lot of people have ideas that differ from reality. Ag flying is a lot of hard and dirty work. Most any operator will be glad to let you take on the duties of loading and wrenching on the aircraft. Very few guys ever land in a seat without first loading and helping to maintain the aircraft. There is no need to complete step one before going on to step two.
Third, develop a plan. Handing over tens of thousands of dollars to a school in hopes that a job will fall in your lap isn't much of a plan. Talk to some operators and see if there is a way that your needs and theirs can be met. It may eventually require going to an ag school, but not always. There are a lot of guys who would love to have a new guy step in with the eventual goal of buying out the flying service. Someone in this position would be more willing to help a novice pilot work into the industry over the period of a few years.
Fourth, be ready for the long haul. For an operator to give someone a chance is a huge risk. The average ag plane for a newer pilot runs well over $300,000 and the insurance doesn't even come close to eliminating the operators risk. Liability is huge, and farmers are intolerant of letting their precious crop be used as a classroom for beginners. For these and other reasons, it takes time for an operator to work a new guy into a seat. For the aspiring ag pilot, it will take three or four seasons to become a safe and productive member of the team.
Fifth, be aware that the flying part is only a small fraction of the skill set needed to become successful. There is a lot to learn about local weather, crops, farmers, public relations, maintenance, specialized electronics, dispersal systems, and especially the responsible use of crop protection materials.