You research managers with good reputations - they aren't regulated
here in the states so some can be quite poor. You research agents
who are willing to read script from new writers.
Then you send query letters to all of them. Then you send query
letters to the agents who don't accecpt new writers - just in case.
In order to maximize your chances of getting an agent, you should
submit to prodCos as well as agents. An option (or better, a sale)
to a prodCo can often do wonders when it comes to finding an
agent. Almost any agent would be happy to take on a client (and
take his 10%) that's already done the legwork and found money for
his work. When sending query letters to prodCos, call ahead of
time and make sure you know how to spell the name of the person
you're sending it to, and what their exact title is. Screenplays
are read and considered by the Development (or Creative)
department. Just call the prodCo and ask the receptionist if they
accept new material... and if they do, to whom you should address
the letter, and what their title is.
You should NEVER send your script (or a treatment or anything
other than the query letter itself) unless the company first asks
for it. Legal reasons prevent companies from accepting or even
looking at material submitted without their express permission or
a pre-existing working relationship. At best, your script (or
treatment or whatever) will be returned to you unopened, or thrown
away. At worst, you'll be put on the company's blacklist and never
allowed to submit anything again. Just send a query letter... if
they want to read your script, they'll ask for it.
The best way to optimize your chances of getting an option or a
sale is to send it to as many people as possible. Agents, if they
like the script, will send it to the prodCos they have connections
with. prodCos, if they like the script, can pay you for your work,
or at least give you the clout to get an agent.