Phrasal verbs (e.g., "break down," "show up") and collocations (e.g., "make a mistake" vs. "do a mistake") are crucial for natural fluency. Create flashcards for common ones and practice using them in dialogues. For example, instead of saying "explain," use "break down" in a sentence: "Can you break down this concept for me?" Listening to podcasts or watching sitcoms helps spot how natives use these phrases effortlessly.