For a reaction to be successful two atoms need to collide with a sufficient amount of energy (activation energy). Raising the temperature increases the amount of kinetic energy that the atoms have, which means that there are more successful collisions so the rate of the reaction increases. Increasing the concentration of the solution causes the atoms to be closer together, this in turn also increases the amount of successful collisions, increasing the rate. Using a catalyst, lowers the activation energy required for a successful reaction, therefore using a catalyst also increases the rate.