At our club (Ostrów-Poland, EPOM) on high-season days it is pretty much assumed "wanna fly, be there all day". No rigid rules though, peer pressure seems to be enough, with much flexibility as long as it is not perceived someone is abusive. It is possible to schedule flights and show up only for that, but somehow those people do not last long if they keep to fly only in that mode. Glider assignment is mainly first come, first served, often with negotiations afterwards. In particular people yield to those who earlier planned significant XC or badge flights. Time is shared within reason, case by case (here there are so many cases, depending on for example a particular pilot's stage of training within current time-frame, that formal rules would be impractical, people seem to agree on informal ones). On very busy days it is probable that latecomers will not fly. People who prepare for competitions (maybe 6 pilots in 80+ membership) have absolute priority and usually have gliders assigned for an exclusive use.

What helps is that the FIs have (by custom and consensus) absolute and arbitrary authority to schedule and recall people.

It is expected that people stay until all operations are over and gliders stowed (or hauled back from outlandings as case might be). Of course not everybody always does, there is sometimes bickering about that, but on the whole it works.

What the system does in practice is that there is always a group of people sitting down for hours on a grass at the launch site (we have a field nearly mile long and about half across), talking shop or just socializing, waiting for their turn. People often come to just hang around (tows are expensive for us, young people in particular have tight budgets and often pass on middling conditions).

Privately owned gliders (perhaps 1/3 of the fleet) get tows mixed within the rest. Not everybody gets always tow at optimal time (double-seaters have priority, same also with some training solo flights) but on the whole it works. Practically all private glider owners are also longtime club members, they went through the system in their "student years", so there are no complaints, though sometimes the grid swells to some 16 ready gliders.