Ideas, like opportunities, don't come that often. We have to look for them. Sometimes, if we're lucky, an idea for a screenplay appears out of nowhere. We're walking our dog, taking a shower, overhearing a conversation in a restaurant or an elevator, skimming the newspaper and voila!...inspiration strikes.
That's cool if that happens, but if we're spending the bulk of our time waiting for that fantastic idea to land in our laps, well, we're going to wait a long time. If the muse isn't striking a chord, we have to look for ideas. How do we do this? Pretty much by making sure our antennae are up 24/7. Be on the look out for ideas from all the different kinds of media. Read newspapers. Read a few of the pop culture websites and blogs.
When you're talking with friends or co-workers or strangers, pay attention to what they say. They might innocently relate an anecdote that resonates with you and could serve as the catalyst for your next script.
Let your mind wonder. Think about your past. People, events, specific incidents that affected you. Sometimes recalling things from our past opens up a door that has long been closed.
And don't forget about reading. Inspiration breads inspiration. Or going to movies. Sometimes watching a film can jump start your creativity.
But the most important thing is to always be ready to be receptive to the random comment, encounter or oddball incident that gets you to think, "What if...?"