If you are the director and/or producer, being early is a must. As a rule of thumb you should be the first one in and last one out.
Another trick to thwart the habitually late cast member is to schedule
his/her scenes later in the day and set their call time an hour earlier
than you normally would. That way your crew is busy doing something
rather than flirting with diabetes with the donuts of the crafty table
while waiting to get started.
The possible downside to this is that if someone begins to catch on that they are doing nothing for the first hour or so, it may encourage them to just arrive later anyway.
The hard truth is that you can often identify your troublesome cast or crew members before the cameras start rolling if they are always late to meetings and rehearsals. It may be a very hard call to make, but if you are on a really tight schedule and can't afford to tack on extra hours (or days) to accommodate people who don't seem to care about making people wait around for them, you may want to consider replacing them before you start shooting.
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