Does your car drive in a straight line? Or does it try and pull you into the kerb or push you to the centre line?
There are so many reasons why your car may not drive in a straight line. It could be as simple as incorrect tyre pressures or it could be a more complex fault.
If you haven't had it checked, then your alignment could be out. Likewise, if you have had it checked and the garage hasn't followed the correct procedure it could also be mal-adjusted. Conventional 'tracking' or 'toe and go' as some people call it is the practice of aligning only the front wheels of the car. This may be fine on a fixed axle go-kart, but in the day of the modern motor car it certainly isn't!
Tracking was useful when car's had very few steering and suspension components that could be adjusted. In the recent past, car suspension has evolved as drivers demand a more comfortable and quieter ride. This demand has seen vehicle suspension develop at an incredible rate and even an average family car will have a complex setup with multiple points of adjustment.
The only way to find out is through a proper four wheel alignment. Four wheel alignment will measure a minimum of 12 angles and compare them against the vehicle manufacturers data. Adjustments can then be made to ensure all four wheels are adjusted and restored to the position they were in when the car left the factory (although some top end wheel aligners will actually do a better job than when the car left the factory)!
You should always get your wheel alignment checked when you have new tyres fitted to ensure you get the best performance and longest life out of your purchase. Alignment should also be checked if any steering or suspension components are replaced or if you have hit a pot hole or kerb. I'm not talking about little scuffs here and there on the kerb, but you know when you have hit something hard.
Always ask the garage what you are getting for your money. Some garages offer 'toe & go' as wheel alignment, as you can see from the information above the two are very different.