Changes in surface area
The bigger the surface area (to volume ratio) the faster the reaction. This is because there are more particles on the surface for the reactants to react with, meaning more collisions with the particles meaning a faster reaction. In a solid, to increase the surface area without decreasing the mass just break up the solid into smaller pieces.
Concentration of solutions
If a solution is very concentrated there are lots of particles for its volume (the particles are close together). More particles means more collisions and therefore a faster reaction rate. Alternatively, if the concentration is very weak there are a very little amount of particles for its volume (the particles are very spaced out). This means collisions will be less frequent (are there are less particles to collide with) so the reaction is slower.
Pressure of gases
This is very similar to concentration of solutions. If the gas is at high pressure there will be more particles squished into a certain space, more particles mean more collisions which mean a faster rate of reaction. Alternatively, low pressure results in little amount of particles in a certain space meaning less collisions (as there are not as many particles to collide with) meaning a slower rate of reaction.
Temperature
The hotter the reactants the faster the reaction. This is because the particles have more energy due to the heat. Because they have more energy this means they will more faster and therefore collide more. Alternatively, the colder the temperature of the reactants the slower the reaction rate. This is because the particles have very little energy.
NOTE: faster collisions are only increased by temperature, all other ways to increase reaction rate increase the amount of particles to collide with.
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