The premise is simple: show up at the track (Batangas Racing Circuit or Subic International Raceway), pay a fixed fee, and then go out on the track as often as you would want. Helmets aren't required, although they are most definitely recommended; they're for your own protection anyway. Renting a timing system is optional, you can also use your own system if you have one. Or the ever reliable stopwatch is more economical solution if procuring a laptimer is too expensive.
Trackdays are different from Run What You Brung events. In trackdays, you really aren't competing against anyone. You're not really looking to be champion; there are no series points to be given away. But the sheer pleasure of driving your own car in such a challenging track as the BRC should be a reward in itself. Also, in a track day, you can drive as many laps as you want. If you want to empty one whole tank of gas then you're welcome to do so. You're also free to come and go as you wish. Some people arrive as early as 7am and leave before lunch time (to avoid the traffic). Others arrive later and stay until late afternoon. It really has a very open and accommodating atmosphere.
Another treat that will greet participants, and those that simply make the trek to racetrack, is the sight of absolutely jaw dropping cars. If you're on your way to the track, don't be surprised if a Porsche 911 suddenly overtakes you on the expressway. Chances are the guy's also going to the track. Lancer Evolutions, Subaru Imprezas, and highly modified Honda Civics are just some of the regular participants of the trackdays. However you do not have to drive a modified car to be able to join. Stock cars can do just fine; in fact there been several completely bone stock cars that have joined already. As with any long journey, you just have to make the usual precautionary check-ups regarding the tires, brakes, radiator/cooling system, etc.