The rate of a chemical reaction can be increased by increasing the surface area of a solid reactant. This can be done by cutting the substance into small pieces, or grindong it into a powder. If the surface area of a reactant in increased: 

• More particles are exposed to the other reactant
• There are more collisions
• The rate rate of reaction increases. 

The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which speeds up rate of reaction but does not get used up during the process.

Only a very small amount of catalyst is needed to increase the rate of reaction between large amounts of reactants.

How does a catalyst speed up a chemical reacion? 
A catalyst speeds up a reaction by providing an alternative reaction pathway for the breaking and reforming of bonds that has a lower activation level. This means that the energy barrier is lower, so more chances of collision. According to the collision theory, this means that the rate of reaction is increased.

Increasing the concetration of a reactant will speed up a chemical reaction because there will be a lot more particles, which means that there will be a lot more collisions taking place, this results in the fact that the rate of reaction increases. 

Increasing the temperature means that the molecules move faster, so they collide more frequently. According to the collision theory, the more frequently molecules collide, the faster the reaction. However, it's not just how frequently they collide, but with how much energy. The hotter it is, the more energy has been converted into kinetic energy of the particles. So, more energy, more movement and thus, more frequent collisions.