You open your story with the protagonist sitting by the windowsill watching the clouds roll by, or standing on the rooftop looking below at the people walking past. This kind of opening does not offer any action or drama. The character is not doing anything to engage the reader. A story must happen to entice the audience. Moreover, your opening paragraph serves to advertise. It attracts a potential reader when browsing at your work. Never miss this opportunity.

Example: Tim Corso sat on the bench in the locker room. He wiped the sweat trickling from his forehead. He was proud of winning the fight. The looks on his wife and young son’s face were priceless. But he had a larger concern: He had double-crossed the mob, and they will go after him. He kept thinking of where to hide his family. 

While the above opening offers a brewing tension and a potential for great drama, the protagonist sits there dilly-dallying on what to do. It may attract readers’ attention, but it will not entice them to get involved. At the rate of the pressure the character is in, he must spring into action. 

Example: Tim Corso punched his locker door, leaving it with a huge dent. He would never embarrass himself in the presence of his wife and son by taking a fall in the most important match of his career. For double-crossing the mob, they will go after him. A fist banged on the door. They were going to kill him. But he will not go down without a fight. He rummaged through his sports bag and pulled out a Beretta.

This is an effective opening. Your character is not rendered static by sitting and thinking of what he is going to do. This makes the reader curious about what will happen next. The character does not receive the action; he is part of creating the action. In the first example, the character wastes too much time in introspection. 

Another passive opening: The banging at the door stopped. Tim checked his pistol’s magazine containing ten rounds. Sweat continued trickling down his face. He was in his mid-thirties. A few more years of boxing and he would retire, provided that he could escape from the mob. He wondered if they were still outside waiting for him.

Too much description and not enough action. Make something happen. Do not put too much emphasis on atmosphere and thoughts. Make it active.

Example: Tim cocked his pistol and wiped the sweat on his forehead. As he slung his bag on his shoulder, the banging at the door continued. “Corso, open up, you asshole! You’re gonna pay!” Tim looked around for an exit and found an air vent. As the fist kept banging on the door, he worked his way through the vent. He had to save his family first.

The description along with the introspection now blends with the action, creating an even flow in narration. The details and character’s thoughts contribute to pushing the story forward.