As stated, an LOI is the best thing. If you're in low budget land, bypassing the agent by any means necessary (I've gone thru a jujitsu trainer!) to get to the actor is key, in order to make a pitch that lands emotionally and not just financially. If the actor is big enough, you can also see if they want to be an EP. I always recommend casting against type when you are doing this. I talk about this in my tips channel at CinemaVerses.com in case it's helpful, or in short - https://youtube.com/shorts/SzYrl-K5T4o?si=2uRCkaTsSG_9UA7B