All tires tend to wear down with time, but if a wheel remains fixed in one specific condition for longer period of time, its condition will decline rapidly. As a rule of thumb, tires should be rotated once in every 3 months or 7000 kilometres, or whatever comes first.
A good practice is to schedule wheel rotation with the change of oil. Rotating tires does not take a great amount of effort and is an inexpensive way to increase the life of your tires. As four tires are in use at a given time, you can use maths to calculate all possible number of rotation sequences possible.
The wear and tear of tires also depend on your style of driving and your environment. If your daily route has a number of flyovers and connecting roads in it, it will cause the tires to degrade rapidly, because when the car moves in semi circles the centrifugal force puts a lot of pressure on the edges of the tires.
You can rotate tires in many ways possible; these are some of the most popular rotation sequences that are used these days.
In this sequence the tires are switched in a diagonal pattern, i.e. the rear left tire is put in place of the front right tire and the same goes for the other side as well. The front tires are placed on the rear of the vehicle on their respective sides.
In this procedure the rear left tire is switched with the front right wheel and vice versa.
Rearward Cross pattern:
This sequence is similar to the forward cross method, with the only difference being that the whole axis is flipped by 180 degrees. It means that the front tires are placed in the back side of the vehicle in an X pattern while the rear tires move to the front side of the car, but they remain on their respective sides.
Front to Rear:
In this pattern, you switch the tires on each side by their counterparts on the other end of the car.
Side to side:
In this sequence the tires are switched in the side way pattern.
Choose any sequence that you find appealing, and place the car on double jack stands. Rotate the tires and take the car off the jack. Take the car out for a drive and feel the difference in its road grip and control.