How to get an agent as a writer

So, you have slaved away at the computer for months, eking out your first script. You hold it in your hands and flick through the pages. Smell it. Smells good, right. That new script smell. What now? Get it produced, right? Find an agent perhaps?
But wait, agents seem interested in the script, you might have even gotten an interview, but it does not ever go further than that. Why?

The tough reality is, you need to go straight back to your computer and start writing your next project.

The more ideas you have, and indeed the more scripts you have completed, the higher your chances of finding an agent.
Agents are almost always busy and inundated with piles of scripts no mortal will ever be able to handle. Therefore you need to help them see why you are worth representing. And nothing says serious, committed writer more than a solid body of work. A short film script or two will get you nowhere, that much is certain.
Even if that one feature film script you have written is amazing, there are a lot of amazing scripts out there from other writers. You will often have stiff competition. And let's be really honest, you are only as good as the hours you put in. More scripts just shows you have worked harder at perfecting your craft.

Max Landis, the son of John Landis, effectively making him Hollywood Royalty, had written no fewer than 40 feature films by the time he sold his first. Now he has about 10 of them in production, and is no doubt churning out more. The industry started caring about his work when he could answer that dreaded, awful, nerve-racking question: 'That's great, what else have you got?'
Every time I have been faced with this question, the memory of Alan Partridge saying 'Monkey Tennis?' is the first thing that springs to mind.

One other thing to keep in mind is that TV is where the good work is right now for writers. Most film scripts never get made, and if they do, it's years of pre production, often ending in the project getting shelved. You need to have other ideas to be working on, rather than pinning all hope to just one. An agent in the meantime will want to get you out there working in the industry, and so more often than not, the first real paying gig will be writing for a long running TV series. It's a good way in. Many serial shows are desperate for good new writers, with talent and fresh ideas. You will help your chances even more with an agent if one of the things you have written, at least to treatment stage, is a drama or a sitcom for example.

Now you have, say, three scripts. The keyboard on your computer is starting to look worn, but your portfolio is looking fat and healthy. This is when the agents will really start to take note. You have gone the distance with writing a script a number of times, proven you can write more than one good script, and for the agent, they need little else to prove to clients that you're the writer for the job.

This is when a writer gets an agent most frequently. Remember that agents are busy people, filling an important function in the industry, and you need to help them seem your potential as much as you can, because they will not have the time to come and look for it.

One final tip, don't be afraid of getting your scripts sent out to competitions. Even one win of some sort helps convince an agent to rep you, because you can show them how others in the industry have had faith in your work already.