Agents don't get excited by writers with one script because they're in this for the long haul. More scripts, more commissions. Protect your completed work. The Writer's Guild is a great resource. You should also register with the US Copyright Office which has all its forms online.
Contacts are everything.
Make sure you get the names spelled correctly, the snail and e-mail addresses, and every phone number you can cajole out of everybody you meet who qualifies as a legitimate contact. If he or she was a working professional, contact number one. Keep in touch. Let them know what projects you're working on and ask them if you can send it along at some point. Maybe they'll pass it along to their agent.