You have the scene planned and are sitting down to write. What are some of the things you need to make sure are in the scene. Remember the scene is about conflict and bringing the focus character into trouble, leaving him or her with a dilemma.
Time unifies the scene. Make sure you set up the structure of time. The scene can occur in minutes or hours or perhaps days. Time unifies the scene. So does viewpoint. Whose eyes are we seeing the scene through. Bouncing from head to head can muddy the scene. Where are your characters located? A house, the great outdoors. Nailing the scene to a place is part of the set up. Then let the reader know why the characters are in this particular place at this particular time.
Make sure the focus character has a goal. Through actions or dialogue you can also show the goal of the other character or characters in the scene.
Build the scene to what is known as the curtain scene. Just like in a play, each act will end with a line that will draw your reader forward. Don't end with the character falling asleep. If they've gone to bed make the curtain line one that will make the reader forget the focus character is escaping into sleep.
Make sure to develop the scene fully. Writing too tight might cause confusion. Keep the story in the present. Putting in a long flashback will pull your reader out of the story. Flashbacks can be used but not an entire scene for that disrupts the forward movement. Use a though or a bit of dialogue to show the past.