Once a year you should have the alignment checked. Look at the tires that have been on the front of the car. On some vehicles especially vans, the outer edge of the front tire may wear more than the rest of the tread. This is because of the manufacturer's suggested caster setting causes the tire to lay over on it's edge when you make a turn. If the tire is an all season and you have a front wheel drive car and the rear tires look like someone took a hot knife and scooped out small pieces of rubber and the shocks are not leaking oil and there is no other symptoms of bad shocks, then the tire is probably at fault.
Car pulls to one side or the other - Proper procedure is to first check the tire inflation.
If that doesn't correct it then the two front tires should be swapped side to side. Spending more money at this point is useless. If the car pulls to the other side, it has to be a tire related pull created by a defective tire. This is one job on your car that will always have symptoms. So, if there is no pulling problem, no abnormal tire wear, then there is no need for an alignment.