Throw a bombshell into the main character's life that forces him to react. The protagonist, who was dealing with problems even before the inciting incident, now suddenly faces a completely unexpected development.
Think of the worst day in your main character's life, or the best day. The inciting incident is the event that sparks the action and sets in motion changes that the protagonist cannot avoid.
Hook the audience with an inciting incident that puts your main character in trouble, thrusts her into an entirely new setting, or forces a drastic change in the character's life. The audience wants to see how the protagonist will deal with the challenge.
Show the protagonist's action in response to the inciting incident. What he does may buy some time. It might make the situation worse. It also tells us about how the main character performs in a crisis and hints at developments to follow as the story unfolds.
Make the stakes high enough and the threat real enough that the character and the audience care.
Bring on the action of the inciting incident as early as possible. Even if you need to set up the lead character's situation first, the inciting incident should happen in the first 10 pages of the screenplay.