Nature of the reaction: anything about a reaction which facilitates efficient contact between the particles falls in this category; among the possibilities: surface area, fewer reactants in the balanced equation, fluid phase, etc.

Catalysts: these are substances which influence the rate of both reactions, forward and reverse; some catalysts appear to work by providing a favorable collision geometry; we don't know how some others work but in each case the activation energy requirement is lowered with the catalyst so a greater proportion of particles will possess it.