There are nearly 8m penalty charge notices (PCNs) issued a year, or one every four seconds. London, not surprisingly, is the parking ticket capital of the UK, followed by Liverpool and Manchester. The cost can be up to £130, although that's halved if you pay within 14 days.

What is surprising is that the worst road for parking tickets is not in central London, but in one of its suburbs. Chiswick High Road in west London has more tickets issued on it than any other road in the UK – 13,000 in 2012. Outside London, Alum Rock Road in Birmingham is worst, while in Scotland it is Chambers Street in Edinburgh.

Around one in four people appeal; of those 40% are successful – but the success rate varies. For example, in 2011 in Bradford only one in 10 won, while in Chichester on the south coast it was nearly three quarters.

When cases end up at the independent adjudicator it is surprising how many are simply not contested. In one six-month period of 2010, Lambeth Council did not bother to contest nearly half of its 2,700 cases.

Money has produced a video on how to fight a parking ticket if you feel it was issued unfairly, available online at theguardian.com/money.

Here we guide you through what you can and can't do. We'll also take a look at what to do if you are hit unfairly by a "private" parking fine, such as being charged for overstaying in a supermarket car park.

Appealing a PCN

After parking your vehicle in what you think is a perfectly legal way, you return to your car and find a ticket or, worse, that you've been clamped. What do you do?

Firstly, if you've got your mobile phone or a camera with you take photos of the car, road signs, road markings and the meter, focusing on anything that is unclear or misleading.

Also, take witness statements at the scene. If, for example, you were loading or unloading within a specified time limit, if there is someone who can corroborate that then obtain a statement from them. Once home, gather together your documents.

Maybe there were mitigating circumstances for your parking offence, such as if your car was broken down, or you had fallen ill, in which case obtain a doctor's note. Councils rarely accept a challenge based on mitigating circumstances, but if there are "compelling" reasons an independent adjudicator can force the council to take them into account.

• Starting the appeal process Broadly, this is the system:

a) make an informal appeal to the council. It fails, so you …

b) make a formal appeal to the council. If that fails, you then …

c) make an appeal to the independent adjudicator.

Make sure at the outset to ask for the fine to be suspended or frozen at the lower level until there is a resolution of the dispute. Most councils will agree but, be warned, some may not.

You can make the initial challenge online or in writing. Doing it online at least helps you keep a dated record of things. Also, make make sure you get your appeal lodged as soon as possible.

• What you can appeal on You can only make a challenge on particular grounds, but the main one is "the contravention did not occur"; in other words, that you weren't actually parking illegally.

For example, if the signs about parking restrictions were unclear, not visible, tampered with etc; that you were legally loading or unloading the car; or that the place wasn't properly marked out as restricted (eg, the yellow lines were not clear).

A common reason why cars are ticketed is that they were outside a marked bay. By law, the bay must measure a minimum of 1.62m from the kerb to the outer edge of the white line, so it may be worth getting out the measuring tape.

There are things that just won't wash, though. Saying you couldn't find anywhere else to park won't work. Unfortunately, saying you went off somewhere to find change for the meter isn't grounds either.

• What happens next

The council will consider your informal appeal, and tends to do so very quickly – usually within two working weeks. If you win, brilliant.

If it rejects your challenge, however, don't give up. The initial rejection is just an informal rejection.

You now have to start the formal process, and what that broadly means is you just submit all the same information again, and it will look at it more seriously. Once again, ask for the fine to be frozen at the reduced rate while you make a formal representation, although at this stage not many councils will agree.

• Going to the independent adjudicator

If you are not successful with your formal representation, the next stage is taking your case to the independent adjudicator, which you have to do within 28 days.

Don't feel overwhelmed about this. The process is free, it's not like a court hearing and you don't even have to attend. You can choose to have a postal or a personal hearing. And remember that it is an independent person examining your case, not the council as judge and jury.

Which adjudicator you go to depends on where you live: for England and Wales (excluding London) it is the TrafficPenaltyTribunal.gov.uk; for Scotland the Scottish Parking Appeals Service (0131 221 0409, no website); for Northern Ireland it is the Courts and Tribunals Service, and for London the Parking and Traffic Appeals Service.

By this time you'll have amassed your evidence and your case, but the adjudicator will have seen nothing of it, so put every last bit of it together, including photographic evidence, and send it along. It won't hurt if you add a separate letter setting out your case.

There is some very useful guidance on the website by adjudicators of past cases and how they ruled, which might help you assemble your case.

The adjudicator will allow or refuse your appeal, but the decision is final and there is no automatic right to appeal, except in exceptional cases.

• Fines for parking on private land

The good news is that since last October, wheel clamping on private land has been banned.

This had turned into a billion-pound-a-year industry with a lot of unscrupulous operators almost extorting cash out of unsuspecting drivers.

If you find your vehicle clamped on private land, call the police– although you can still be charged.

Recently, Money ran a story about a man who pulled into a motorway service station, dozed off for a few hours, only to later receive a fine of £90 for exceeding the maximum two-hour stay.

If you consider that you didn't break the rules, they weren't clear, or you had an emergency to deal with, you can challenge a private parking ticket. You can also challenge it if the amount you are being asked to pay is unfair.

If you refuse to pay, this is a civil matter, and all they can do is seek to recover the money through the small claims court. However, they do have access to your address and car details through the DVLA.

The key thing to remember is that under contract law, a private firm can only claim for the loss they have suffered because of your offence.

They may try to claim a penalty of, say, £100, but in law they may only be entitled to any lost revenue. So, if you pay £2 to park for one hour but stay for three, they can only claim for two hours of lost revenue, which is £4.

Appealing a private fine

There is now a new body called Popla, the Parking on Private Land Appeals service, which will handle appeals against fines on private land.

The process is actually very similar to that for an official penalty charge notice – you contact the organisation that issued the parking charge in the first instance and appeal to them – first informally and then formally. If that fails, appeal to Popla.

Prevention is better than cure

Park correctly in the first place. Park-up is one website worth looking at to find free parking spaces, although it only works in London.

In Manchester, the city council is trialling a smartphone app that will tell you where and when parking spaces come free, and even direct you there.