Remember that old adage: a picture is worth a thousand words. Never is this more true than with screenwriting. And if you let your "pictures" do the talking, you can greatly cut down your words. Remember, screenplays today are rarely longer than 110 pages. You might think that you're writing the next three-hour-long dramatic Oscar winner, but if you're a first-time screenwriter, you have a much better bet of selling your screenplay (or even getting it read in the first place), if you adhere to some industry standards. And you do want to sell your screenplay, right?
One of the main problems I often see with beginning screenwriters is that they attempt to tell their story through dialogue instead of images. There is too much talking about what is going to happen and not enough just cutting to the action.
One tip for beginner screenwriters is to write a scene using only images to tell the story. An example of this is: instead of having a scene with the main character addressing her brother in order to let the viewer know she has a family, instead get it across quickly with a closeup of a family photo while the main character is doing something else that is necessary to the telling of this story. The viewer is very savvy. You'd be amazed how much of the story is told just through images. Why do you think that a foreign film can be so gripping? As so much gets "lost in translation", why not fall back on the universal medium for telling stories: imagery.
And like I said, don't have characters talking about what they are going to do. For example, two characters say to one another, "Hey, wouldn't it be great to go to the horsetrack today?" "Yeah, sure, let's do that." Get rid of that! Just cut to the horsetrack. You could even end the previous scene on some kind of "button" that humorously or dramatically gives a reason for why these two characters have to go to the horsetrack. For example, one of the characters says, "God, I'm low on cash today." Then you cut to the horsetrack. If this is a comedy, this will lend humor to the movie, as we all know how hard it is to make money gambling. And if this is a drama, it will lend pathos. Perhaps the main character needs money for his family, but his major flaw is continually hoping to make money the easy way, and, as a result, his family suffers.