Technically, esterification doesn't need any "special" conditions to proceed. If the reactants are just left there, they'll produce the ester (which in your case will be ethyl hexanoate) and water. However, because this process is slow, we use reflux (the gentle heating of the reactants, with the vapours of these reactants condensing and dripping back into the reaction vessel so as to stop the escape of these reactants) so that esterification goes more quickly - naturally, since heating any reaction gives the particles more kinetic energy and a greater chance of colliding successfully to form the products. A sulfuric acid catalyst is also used to increase the rate of reaction, decrease the activation energy needed for esterification to occur and also as a dehydrating agent. As it "sucks" or absorbs the water, a product of esterification, the equilibrium shifts right to favour the formation of more water and by doing so, favour the formation of more ester.
Sorry if that was confusing.