Okay, so you're sitting in your chair, staring at the screen, and nothing is happening. Nothing. Nada. Zilch. What can you do to jumpstart the flow of ideas?
Actually, there are several things:
Read. Everytime I'm stuck I pick up a book and start reading. I don't know why it works, it just does. While I'm reading, my brain is working out the solution to whatever problem I'm having at the time. 99% of the time this works.
Question everything in the scene. Even if you're not a plotter (like me) you can ask yourself questions about the situation or scene you're stuck in. One of my crit partners is writing a historical. She's a panster. And even though we've hashed out the plot a dozen times with her, she doesn't write it down and forgets or decides to change the basic plot in some way, so she either ends up getting stuck or taking a different direction and writing herself into a corner. But that's a whole other discussion. Anyway, the H/H in her story were stuck in a store and she couldn't get them out. So they stayed there for a loooong time while she griped and complained and sighed. Then came to our next meeting with a previously written scene she had polished. I kept saying, "When are these two going to leave the *&%$% store?"
Her answer--I don't know. So we started asking questions. (They H/H had ducked into a store, shop, whatever, to avoid someone they didn't want to meet up with.)
What's the purpose of this scene?
Why didn't they want to meet up with said person?
What's the worst thing that could happen to them at this point?
Is the Heroine content to blindly follow him without demanding an explaination?
Can you use this scene to show yet another of the Hero's many layers? His skill as a spy?
How will this impact their relationship?
Plot/outline. Go back to your outline or plot and decide what--logically--should come next. For every action, there is a reaction or consequence. If the H/H are in the store, then obviously they have to leave. Out the front? Out the back? Who decides? Why? Consequence or complication resulting from the impulsive decision to hide in the store?
Shake things up. Are they going to TALK to each other or just stand there? Take them out of their comfort zone. A person's true character comes out during times of stress. This is a good place for one of the characters to say/do something that will leave one or both questioning their own beliefs, assumptions, the status quo. If nothing changes as a result of them being in this store, then they shouldn't be there.
These are just a few of the things you can try, but I can tell you I've used them all and have found them to be helpful.