What does the protagonist want? Why is it important? Who (antagonist) is stopping her from getting it?
If you can answer those questions, and show the protagonist and antagonist in a struggle (verbal or physical), then you'll have tension in the scene.
If you've got the protagonist and antagonist in a struggle, then look at the "beats" of the struggle, and make sure they're getting more intense. For example, if the protagonist wants to go see a foreign flick, and the antagonist wants to go see the latest action flick, it starts out with the protagonist saying "let's go see this foreign flick," and the antagonist saying "I'd rather go see this action flick." That's the initial beat, and then the next beat is when the protagonist tries something different, perhaps bargaining, to show how important it is to him: "if you go to the foreign flick with me tonight, I'll go to two action flicks with you tomorrow." And she says, "Nah, I'd rather go to the action flick with another guy that I'm thinking about replacing you with," and the tension has escalated in this beat, b/c she's now thrown their relationship's future into the mix. And he says, "If you go out with another guy, our relationship is over," which is another escalation. And this whole example is pretty silly, but I'm just trying to show the conflict escalating, instead of going round and round (as people do in real life) at the same level of one person saying X and the other person saying no to X, and then the first person makes the same demand, without increasing the stakes, and the second person says no again, and so on, without an escalation.
As a little trick, if you've got the protagonist and antagonist, and the beats that are escalating, and you still want to ramp it up a little, setting a time limit often helps, like the 24 hours of the tv show 24. You'll see it in a lot of suspense/mystery shows/novels, where there's a clock ticking in some form -- the bomb will go off in 24 hours or the execution will happen in twelve hours, or the trial will start in 2 days or the serial killer will strike again tonight if he's not captured, or the boyfriend is moving to the other side of the world next week, or whatever. It verges on cliche, but it can be done subtly, and if it's become a cliche, it's because it works.
JD