Most states require some college education. Even if it is not required, a solid background in wildlife management, forestry, environmental science are good choices. In addition, police science and public speaking are helpful.
Physical fitness is a plus, as well as practical knowledge and experience in hunting and fishing.
Also, be knowledgeable of the wildlife laws of the state you are interested in. Individuals that have served in the military gain much experience and an advantage in civil service considerations. Experience serving as a law enforcement officer is sometimes given consideration. In Pennsylvania, there are volunteers called Deputy Wildlife Conservation Officers and Deputy Waterways Conservation Officers. Individuals that have experience as a deputies, increase their chances for being selected in a highly competitive testing program for selection as conservation officers.