Speaking as someone who has worked professionally as a director, producer, Production Coordinator and actor (and helped out on set for friends in a myriad of other crew roles, as well as making my own passion projects) here in Australia and in the UK, here’s my two cents.
First - is every cast member on set where you are filming (ie. Actually in the room where you’re shooting) at the same time, even if they’re not needed? If so, this isn’t great, because, as we know, filmmaking can be very boring and actors are only human and like to chat. My suggestion if its possible where you are filming, is to have a seperate room or enclosed space (to control sound transfer and distraction for those filming) away from where you are filming (the further the better) where cast can hang out and talk to their heart’s content until an AD calls them to set. This is called a “Green Room” in theatre and film and every production will have one to avoid this kind of problem (unless you have the big bucks and can give them their own trailers or dressing rooms!). That should remove excess people off set who don’t need to be present during filming and reduce the amount of chit chat as a result. Rule is: if they’re not in the scene - they stay in the Green Room until called in by a crew member. It doesn’t have to be fancy. Just a room with some coffee and a few chairs. I put a craft table with snacks and water in mine when running set because food is a great draw and also helps to keep their blood sugar regulated and keeps them hydrated (this also means crew will drop by when they have a clear moment and makes cast feel like they haven’t been forgotten and are still part of it all). It also makes them feel special that they have their own area and are being looked after.
A lot of other people here have already mentioned the “Quiet On Set!” call - absolutely correct proceedure. Its done EVERYWHERE on every set and isn’t just said for the benefit of those in the room, but loudly enough for other crew and cast in the nearby area so they know that sound is running and to shut up so you can get the take.
Second: actors are known to question direction sometimes, particularly if they feel its a collaborative space (and you want them to in my opinion, because sometimes they come up with great stuff you haven’t thought of and it makes things more enjoyable). How I deal with this is to compromise. I ask them to do it the way I’m requesting and then we’ll do one take the way they want. It saves time arguing, they feel like they’ve been heard and then you have choices in the edit. Win/win. NEVER take it personally in the moment if an actor does this - even if it feels they are challenging your authority and vision. (You can complain about it when you’re off set, back at home to your flatmate/partner/dog/cat,etc but try to set the example and always be professional in your work when at work). If you can’t articulate why you need something a certain way clearly and respectfully, or they just won’t listen, then that’s also the solution in my experience (and then think carefully before having them back in set for other projects if they’ve been dismissive or rude in any way during this encounter, because that’s EXTREMELY unprofessional if they’re just pulling a power play for their own ego). Sometimes an actor just won’t do something and you have to think on your feet about how you’re going to work around it to make the scene work, but as long as they’ve had scripts in advance and know what’s meant to happen in a scene, they have no excuse to refuse to do something on the day. A rehearsal day also helps iron these issues out before the shoot (fyi for future reference) - that’s why network dramas and large feature films always schedule rehearsals as well - saves time on set.
Lastly - they shouldn’t be turning up late. That’s just not professional. You are paying them (doesn’t matter how much - you’re still paying them!!) Even if they were doing it for the love of it only, they should still be there on time. Are you staggering their call times? If an actor is being called to set and then finds out they’re not needed on set to work for another 4 or more hours, that will cause a feeling of resentment, particularly on low/no pay gigs. Usual rule of thumb is find out from your Make Up artist how long they need with each actor before they are needed on set, then add 45 minutes to that time for wardrobe and a chance to grab a coffee/tea/whatever. Average rule of thumb is a call time of no more than 2 hours before they’re needed on set (depending on make up requirements). You’re not running a social club, your making a web series/proof of concept/film/screen project of some description, so they don’t need socialising time. The wrap party is the social part of the process and they can socialise with whomever else is waiting to head to set in the Green Room or at lunch or other meal breaks.
If you are already doing this calculation of call times and still have a problem, then just schedule them half an hour earlier than they need to be there to ensure they’re on time, or only 10 mins late. Are you doing detailed call sheets? If not, then start. It engenders a sense of confidence in everyone that the production is organised if you do. Rule of thumb - Unit (known as Craft Services in the US) is on set first to set up coffee/breakfast and the cast/crew waiting area and then make up/wardrobe department half an hour later (if you have one) then cast on staggered call and camera/sound/everyone else. There are plenty of examples of call sheets online if you don’t already have one.
In regards to fun on set. Of course people should enjoy working on these things, BUT - it’s no longer fun if it starts to feel disorganised, if you’re not able to get the shots on time and on schedule and if people start feeling disrespected. Doing everything I’ve suggested will help build a framework so everyone CAN have fun and feel like they’re really achieving something
Oh, and finally- NEVER yell at cast and crew (or anyone else). If you’re yelling, it shows you have lost control of the situation (and yourself) and things will just get worse (or people will leave, regardless of contracts and you don’t want that at this stage as it will totally disrupt filming!)
Hope that helps and good luck!