Although you don’t want to write a page-long paragraph describing a room, what you do want is prose that will bring to life the events in your story.
Is there a thunderstorm in your book? Describe it so that your readers can visualize a streak of lightning, hear the crack of thunder, and see a steady downpour of rain. If the storm is intense let your reader feel its intensity through your words.
Is there a fight in your book? Let your reader hear the clatter of colliding blades and the pop of gunfire. Help them to see the blood and sense the agony. Describe how a character moves so they feel as though they are beside him/her on the battlefield.
Do your main characters share a kiss? Make the readers feel as though they are receiving that kiss and not just reading about it. Tell your readers about their rising heart rates, the flavors they taste from each other’s mouths, and the eagerness of their hands.
TIP: To write good prose use the five senses (though not all at one):
And don’t forget that adjectives are your friends! (Just don't go overboard.)