Time is by far the best and fairest way.

Thats how it is at Faldingworth Live and it seems to work. Not all performers like the time slot style, but hey you can't please everybody.

Occasioanlly the MC makes a mistake, or the performer thinks the MC has made a mistake. However most performers are grown up enough to accept the MC's decision so to speak.

In the 4/5 years at Faldingworth Live (originnally Market Rasen Folk Club) only had one person F'ing and blinding, becuase he thought I had brought him off early. It was very unpleasant but got sorted.