My #1 tip for DMs looking to improve is to only make your players roll when you feel that their character would struggle at doing the action. For example, the Ranger is lighting a fire when setting up camp in the wilderness, making them roll a survival check wouldn't make much sense and would only slow down the game. But in a situation where a rogue is picking someone's pockets, obviously make them roll a sleight of hand check because failure could actually progress the story and not slow it down.