It wasn't so long ago that to get on a race circuit you would require a racing licence. But now most circuits are being opened to the public who are able to take almost any road vehicle onto the track.
This is more than likely due to the fact that most racing circuits would be unused for most of the year and so weren't bringing in any revenue. During the 1980s car manufacturer track days became popular where, for instance, BMW would organise a corporate day for employees and customers. Then it moved to corporate event days. From there it was only a short step to allowing the motoring enthusiast access to the track.
Companies realised that there was a growing need for organised events where somebody could pay a given amount, turn up at the track, have a good blast round for the day, and then go home. The fact that modern cars, even standard saloons, have much greater abilities than can be used on the public roads helps to fuel the desire to see what it can really do on a track.
Manufacturers will often promote, say, a rally prepared version of a car in order to sell the more mundane models. Porsche themselves started doing this in their early years having great success in motorsport made them able to sell their road cars. And of course most Porsches are easily capable of taking a trackday in its stride.
Generally roadworthy, if it has an MOT that would be a basic check to make sure it's safe. At the first level of trackday (novice) you don't need any alterations to the car. But just make sure that the brake fluid has been renewed in the past 2 years and that your brake pads aren't on the limit. This is just the most basic stuff. You will need a helmet, which can usually be hired on the day.
For trackdays make sure that anything loose in the
car has been secured as cornering speeds will tend to move things around
in the car, and this could cause a distraction or in the worst case something
could get stuck under the brake pedal.
A good comfortable driving position is recommended so that you have easy
access to all the controls.
If on normal road tyres then you don't necessarily need to alter the pressures. Higher pressures will help to bolster the tyre wall for more stable cornering and after a few hot laps the tyre pressure will increase due to the heat generated. So it's a case of just checking that they don't get too high so that the contact surface alters too much.
As a novice first track day I would recommend doing maybe six to ten laps at a time. Then checking the car over, brake hoses, tyres, brakes etc. It will also give the car time to cool down a bit. In particular the brakes.
When you first go onto a track it will be a bit daunting. Most people will be nervous and the first thoughts are will I spin off the track, will I ruin my tyres, will I ruin my brakes. On a first track day all of this shouldn't be an issue. Because you'd only be doing probably motorway speeds and driving within your own and the cars limits you shouldn't be doing anything that will cause any of these problems.
Certainly in the first half of the trackday when you will still be getting familiar with the track and the driving lines. And that is the real key to a successful track day. Learning how to get the car around the circuit smoothly and efficiently. The best way to do this is to pick a trackday company that has instructors on hand. This is by far the cheapest way of getting round a circuit quickly and improving your lap times and smoothness on the track.
One of the key things I learned about the physics of track driving was that you have to think of the weight, or centre of gravity, of a car as being like a pendulum. So the pendulum will move around the car and have an effect on the tyres and what they can cope with.
With the advent of trackdays more and more car manufacturers are now producing specialist cars for use on the track.
These cars are normally very lightweight, have large efficient brakes and a good healthy power to weight ration ensuring good acceleration. Generally ebing lightweight will give good cornering and braking performance as well.
Some of these cars are built only for use on the track but some of them are for dual use on the road and on the track as well. This means that a car can be driven to the track because it is road legal. The suspension may be slightly harder than a standard road car but the owner will normally have considered this in his choice of 'track weapon'.