Many times in a scene, you are presented with an active choice and an inactive choice. An Active Choice is one that creates action rather than blocks action.

Example

For example, you're in a scene at the DMV. The clerk wants to see your driver's license. The inactive choice would be to say that you don't have it. The active choice would be to whip it out and offer it to the clerk.

The Active Choice opens many new directions to explore by Adding Information. You can Yes And by saying that the hair color is wrong now that you dyed your hair, so you need the card modified. Or you could complain that the picture is too beautiful and you need it toned down a bit since you're getting so many dates from highway patrolmen.

Now your scene partner can Yes And your hair-color change by adding that your hair is punk orange, leading to the discovery that you perform slam poetry for a living. You demonstrate with a poem about standing in line at the DMV. Or, the latest cop who decided against giving you a speeding ticket can enter the scene and be mesmerized by your driver's license but not by your real face.

You can't know any of these possible directions when you whip out your driver's license. You just know that even the tiniest concrete action opens up vast potential that can be reached very quickly.

Whereas, not having your driver's license just means that nothing is happening yet.

Don't inactive choices create comedy and suspense?

It might be tempting, in a scene set in a forest, when a character proposes starting a fire to keep warm, to think of reasons to not get started, like: "We don't have any matches" or "There's no wood! (in a forest, ha ha, get it)."

People do laugh at that sort of response. They laugh for the same reason they laugh at someone slipping on a banana peel. Except they're laughing at the way one player fouled up another player, not the way one character fouled up another character. The problem is, the scene is dead. In a few seconds, you go from an attention-holding scene to two people standing on stage desperately trying to think of something funny to say. The pressure you feel at that moment is horrible. With the reality gone, you know you've got no basis for humor, yet the need to get a laugh grows stronger by the second... (See Gagging.)

A good Exercise is to do a couple scenes of nothing but inactive choices: every response must present something that prevents action; then do a couple scenes where every response must start or continue action. It's actually very easy to think of active choices. It's just a bit uncomfortable until you get used to it (see Improv vs. Instinct).

Be careful not to confuse Disrupting a Routine with making an inactive choice. Disrupting a Routine does indeed create comedy and suspense in a way that works wonderfully in improv.