Hi PbG3! Welcome.
I can share a bit of my own experience on that subject, and I hope it helps.
I have a number of spec scripts written, one a finalist in a contest, one optioned, never produced and I was a judge for three years for a screenwriting contest. I'm just giving you a bit of my background so that you know I have some experience. I don't know how long you've been at this but I suggest that you go out and network in film or entertainment business related events. Getting to know people and letting them know you is the beginning of the process. I believe that in the film industry is mostly about who you know. So go out and network, network, network!!!
You will find that unlike literary agents, script agents do not bother to reply to your queries. Why? Because everybody is writing a screenplay and the chances of finding somebody who knows how to do it properly are slim.
The other thing an agent would want to find in you to take you as a client is your knowledge in the market and the genre you'd like to be known for.
I know it sounds ominous but unless you have a direct connection to somebody in the film industry that can get your script read it could be a long process. If you believe that you have a solid well written script, submit it to contests and see how you place. Scriptapalooza is a good one or the Nichols. That option can help open doors.
I hope I was able to help you.
Just keep going and keep writing!!!