When parking your car either on a public road or in a car park be sure to check a) that you are legally allowed to park there and b) that you are aware of the time limits or charges.
If you have parked somewhere for too long or illegally parked then you can expect to get a parking ticket. There are two main types of tickets, one that is issued by the council / local authority and one that is issued by a private companies. The laws regarding these two types of tickets differs substantially so if you have received one, it is advised that you check who the issuing party is. Some private companies are not actually legally allowed to enforce the ticket they have given you, but always check with a solicitor if in doubt.
If you have a genuine reason as to why you believe the ticket should not have been issued, then with all tickets you have the right to appeal. Make sure you do this within the specified time and that you provide as much evidence as possible to back up your argument.