How do you know if you mess up your alignment on your car?

The safe way is to look at your tires. If they're wearing more on the inside or outside of the tire than in the center it can mean your alignment and/or your suspension is out. My old man would tell you the dangerous way, which is to let go of the steering wheel briefly and see if the car pulls to one side. The tire inspection is the best way to go. You can learn a lot from your tires! A good tire dealer will be able to tell you.