Hello,
Im still in pre-production (I haven't even begun writing the script, Im just planning it out for now)
However, when I am finished and happy with the script I do plan on shooting the short film, but Im only 15, how am I suppose to get actors and actresses to take me seriously as a young filmmaker and be in my movie? Where do I go to hold a free open casting call?
Any help is greatly appreciated

well, usually when you're that young starting off, i'd say getting either your friends or family to star in it, just for the first one though.

So after I make my first one....then what!?

Well, the truth is, to be taken seriously you have to prove that you have previously done seriously good work. To this, you need actors. It's a chicken before the egg thing, unfortunately!

Do the best you can with your friends (have them play roles they can do) - and work up slowly.

Well, I'm only 14, but I always experience the same thing that you are now.

While it's true, there are some plus sides to having your friends act in your film, keep in mind that they may not want to work all the time. The very first "big" time I shot (or, the first one I didn't use my family and was longer than five minutes), I used all my from school to act in it. We were all on the set for five hours, we got fifteen minutes of footage, and I got three minutes of the final cut. Three out of approx. 35.

So, if you are going to use your friends, you should probably plan on finding many, many day sthat you can shoot.

Two words.... Provide...Food..

One thing you could do to increase the quality of acting is to try to get involved in local community theater and then ask some of the people involved if they could act in a short film. Usually, in my experience, most people were glad to help, but just make sure to work around their schedules as they usually have day jobs. Hope that helps.