Do you do a head count, through your ASM (or otherwise) to insure everybody who is supposed to be there IS there?
Do you only check to see that only leading or supporting players are ready to go?
Do you only check that actors who are onstage when the "curtain" goes up or who enter immediately are present?
If I have an ASM, he or she will give me a head count of those who need to go on within the first few minutes, or those actors who like to be present at places. If I don't have an ASM, I assign crew members to do the same.
Do you let your company know that 2 minutes (or 3 minutes, or whatever is standard for the space you work in) after you call "Places, please" the show will begin and it is THEIR responsibility to be in place and ready to go, that you will not hold for them or even check on them, and that THEY must communicate with YOU if they are going to late to their place for any reason?
On the sign in sheet for the first tech, I explain how my preshow sequence is called. Half-hour at 30 to curtain, 15 at 15 to curtain, etc. 3 minutes to curtain is my standard places call. I've never thought it necessary to tell the actors it's their responsibility; I'd hope they'd assume that was part of their job.
Or, do you do something else entirely?
I SM'd
The Music Man this summer and we had a cast of 40 kids, ages 9 - 18. I thought to myself, "How the hell am I gonna keep 40 kids straight with two green ASMs?" At intermission, I made them go to the green room and pick up an index card with a number and their name printed on it (alphabetically, beginning with 1, of course). They all had to enter the stage by the same stairwell so I posted a crew member at the bottom and as they passed by, they handed the crew member their card. He read off the numbers to me and I checked them off a list. I knew immediately who was missing, and intermission never ran over.
Does it vary depending on the cast or production?
Except for the above, no.
And, if you do a headcount, what do you use as you criteria as to who should be present at "Places" call before you begin the Act?
I assume anyone entering on the first or second page and anyone entering within two minutes of curtain and then, depending on the script, I ask if anyone else would like to be counted at places.