There is no need to have a cars wheels aligned on a regular bases. It is a good idea though to have the alignment checked when installing new tires to prevent excess wear on the tires.
You should have wheel alignment done on your vehicle annually or whenever your wheels feel to be out of alighment while you're driving. If it's something you can feel that your car is out of alignment it is important to have it looked at and corrected as soon as possible.
Check your tires. The tread should wear evenly. The steering wheel should not "pull to one side or the other." If either of these is not correct then an alignment is needed.
When your steering wheel is out of wack with your driving
Before-a bad alignment cannot "unbalance" a wheel, but an unbalanced wheel, if bad enough, can throw off an alignment.
you should have a 4 wheel alignment done
Unless you are having tire wear problems or the vehicle pulls to one side, you should only need an alignment check when buying new tires.
Usually a 4-wheel alignment costs between $60 & $90
Wheel alignment coupons can be found at Retailmenot.com, Coupons.com Sadiesaves.com and Groupon. You might also check your local Sunday newspaper for coupons.
Check with your local tire shops. With some shops alignment is free with any tire purchase. Others charge aprox $80 for a standard front end alignment.
Anytime after an accident.
The wheel alignment specs should compensate for crown in the road. The settings should be 2.54/2.73 for the caster and +.21/-.04 for the camber. The toe should be 1/16".
Not necessarily. If the car was in alignment prior to getting the new tires, it will be in alignment after the new tires. It isn't a bad idea to check the alignment periodically and it is probably better to check it more frequently than when you get new tires.