If you're planning on filming something, you'll likely need to cast some folks. I am going to speak more specifically about casting actors for ease, but hopefully most of what I say applies to employing crew members as well
Perhaps the easiest tip I could give you is probably the most difficult one as well. I love working with my friends. I want to have fun filming, and I want it to be easy so it's enjoyable. In my opinion, if you can build relationships with actors then you'll be on your way. How do you do this? Well, it completely depends on you and what sort of person you are. But if you can cast your 'friends', then it'll save you a tonne of time and stress having to cast-from-scratch each time you start a new project. I need to unpack this a little bit, because it may sound lazy. I only cast my 'friends' when they are 100% right for the role. I never do it just for the sake of doing it. But at the same time, I will likely cast a friend over an unknown, purely because filmmaking is a stressful endeavour so I want to know I can rely on that person. Whenever I cast someone who I've never worked with before, there is always an element of unknown that worries me. They're a question mark. 99 times outta 100 it goes fine, but occasionally, you can regret the decision. Ultimately, as a producer/filmmaker, what you should/need/could do is form lasting relationships with the people you intend to work with. The work will benefit, I promise you. You see it was well-known filmmakers and producers (Roger Deakins has worked with the same gaffer for most of his career). It's frustrating for the rest of us, but they often rely on people they've worked with before. This is likely for the reasons I've just detailed. But before you throw your dummy out, if they are professionals, I repeat, they will only cast that person if they are right for the role. But from a filmmakers point-of-view, you want to work with your friends. Obviously.
When it comes to casting my own projects, there is a certain way that I've found works for me. Everyone does it slightly differently, and as long as you get the results you want, there is no 'only-way' to casting your project. Personally, I post online. I detail the project and the role I am looking for, remembering that just over minimum-wage isn't that attractive, especially if they've never heard of me (if you're not paying, things become exponentially harder), so I take some time to make sure the project sounds professional and worthwhile. Recently I've set up a new website so people can apply directly - just incase someone doesn't belong to one of paid subscription sites I've used. I then wait a couple of days until I've had a few hundred applicants (if you're not getting this many, you probably need to ask yourself why not). And then I will try and send an email to every single one of them detailing my process and to explain what happens next. This is a huge, huge, piece of advice I hope you take on board if you don't already do it. If someone has taken the time to read your script and apply, the least you could do is touch-base and let them know when they can expect to hear from you again (good or bad news, it shouldn't matter - let the applicant know!). I hate being ignored, and it says a lot about a production if they don't take the time to do this. Once I've got a healthy number of applicants, I will sift through them and get rid of any unsuitable applicants. Once I've got it to a manageable number, I will sit and watch the showreels. I will then whittle down the applicants into my favourite 10 or so (if I'm lucky) and ask them to self-tape a scene from the script. I typically put a deadline on this just to avoid anyone dropping a self-tape a month later. From there, I will pick a handful I meet for a coffee and make my decision based on all the info I have at that time. This system works for me. It's simple, efficient and quick. Plus I get to drink a lot of coffee.
Show some curtesy
I already mentioned this briefly in the previous point, but I just want to reiterate it's important by drawing a thick line under it. Admittedly, this is something that is quite difficult to get right, especially because it takes up extra time that perhaps you didn't schedule. But just consider how frustrating it is if you were to spend a few minutes out of your day to read a script, apply, to then hear nothing back as though the project never existed. How would you feel? Even if you deliver bad news (they didn't get the role) it is far better than never replying - plus actors are actors, they're used to it, so get over yourself. You could argue that well, it's just one of a hundred roles they've applied for that day, why bother? I don't care! You've got to be the change you want to see, so treat the applicants how you'd like to be treated. Also, how someone treats me over email and during our initial correspondence tells me everything I need to know about the project and how it will run. If I don't hear back for a few days, I know it will be poorly managed. If they appear rude, the experience will be horrible. If they're kind and polite, then guess what? The project will be probably go well. I feel I am a good judge of character, so to an extent, you have to make up your own mind. But if a production is respectful to me, and takes the time to reply and keep me updated, it is so greatly appreciated. I know some of the tricks production teams play, and so I never get my hopes up even if it seems like the job is mine - typically, a producer will have 2/3 people lined up for the role, and so they'll probably be trying to see who they can get for the cheapest. Countless times I've been on the verge of clearing my schedule for a gig to be informed that "I didn't get it" - it's like, wow! Okay. I didn't realise that you were chatting with other applicants because it sounded like the job was mine. So also be clear and honest with your prompt replies - don't lie or bend the truth. I always tell the applicant that they are one of ten or so people I am looking at. It just keeps everything ticking over nicely and everyone aware of the situation.
Lessons for an actor
If you're an actor, here is the section for you. There are so many things you could be doing right, and equally as many you could be doing wrong. If you're getting gigs regularly, then congrats! You're probably doing more right than wrong. But if you're struggle to get the door open, then perhaps you need to look at your strategy a bit more. The honest truth is that most of time you're simply not right for the role. When I look at showreels, I am looking for a sign of the character I've written - it could be mannerisms, hair colour, tone of voice etc. so what are the chances it's you? If you accept that you're probably not right for the role, it will help you to maintain a healthy relationship with the industry. Just because you're in the age-range doesn't meant the role is for you. Personally I think every actor should cast something just to see what I mean. The last thing I cast for, I received over 300 applicants, and guess what? I felt that only 5 were somewhat suitable. There are many reasons why someone may not be suitable, but if you can understand that most of the time it has nothing to do with your ability, then you can crack on with the next opportunity. The next important point to consider is be patient. It doesn't happen often, because I think most of us know it's unprofessional, but people will attempt to contact me directly (via whatsapp, email, facebook etc.) in order to discuss the job/role. I find this increasingly annoying purely because I don't want to be bombarded at all times of the day, and it reeks of desperation. Not good. But perhaps more importantly, I have a system that I like to keep to - it's organised. If you decide to email me and you haven't been instructed to do so, you may feel you are being smart - getting one up on your opponents. But the chances are you are wasting your time because I've got hundreds of applicants to sift through, and your attempt at contacting me will be ignored. Sorry! But I'm just trying to help you. Be patient, cross your fingers, and keep applying.
I don't like auditions. There I said it! If you are casting for theatre, I think it's slightly different as you want to see the person in the flesh. But for me, an audition process never offers something that I didn't otherwise know from watching a showreel. Because at the end of the day, I want to see you screen-acting, not live-in-the-moment-acting. The counter argument is obvious, so before you throw some frustrated angry-ness towards me, just consider my point. Has someone ever blown you away in the audition room you weren't already interested in? If it's a low-budget production the chances are no. If it's an open audition, then maybe - it's just the nature of the set up because perhaps you haven't looked at any showreels yet. But for me, what I like to do is whittle my favourite applicants down to a manageable number (say 3) and then meet them for a coffee. I already know they can act, now I want to see if we are going to get on. I am certain that I can get a sense of a person from meeting them in an informal way. From this I judge whether they are the character, or perhaps, whether the character is in them somewhere. Because for me, that's all directing is: good casting. I don't want to have to work to get a character-performance out of you. I want to tweak who you are because perhaps you've misinterpreted a beat or intention. An audition is a performance. It's not real. Like exams, some people are just bad at them, but it doesn't mean that they're stupid.
Lastly, remember that you are an employer
It's easy to forget amongst all the niceties that you are in fact an employer and therefore you need to take responsibility for being one. Regardless of how inexperienced you are, if you are 'employing' someone to do a role, you need to take responsibility for that. You can't treat someone badly or discard them at will (I mean you can, but I suggest you don't), unless you want the repercussions of your behaviour to be known - because I have no doubt, you will be found out. I hear stories all the time, people talk. You may think you're getting away with it, but you're not. I guarantee in a few years time when you try to cast something and you don't get any responses, your unprofessional behaviour is to blame. I've had my fair share of encounters, and I've passed on the warning to anyone who asks. I am honest and fair with my assessment, but I always remember.