Whether your're writing a novel or a screenplay the heart of story-telling is conflict. When it's hero vs. villain that's easy, but not every story has those. In the more realistic plots, as in life, the biggest enemy we have tends to be ourself.
On her blog, Janice Hardy listed some of the main ways characters make bad decisions:
making a poor decision under pressure
assuming they know it all - arrogance
not considering all the options
not asking for advice
not having alternative plans
Another way to come up with choices is to consider the ways your character might respond depending on what emotion they're experiencing. Here are some that typically lead to conflict:
Use your knowledge of the character to decide which of these (or another emotion) your character would experience in the situation you've created, and then what behaviour might come from that emotion.
(For more information about how to create characters and plots, see my book, "Your Writing Coach," published by Nicholas Brealey and available from Amazon or your other favorite bookseller.)