Long suits are often the most fruitful way to set up tricks. Train your eyes to go straight to the 5+ card suits and think: can I set that suit up? Even 4-card suits (4-3 fits) can create extra winners if the suit breaks 4-3-3-3.
Being aware of these long suits is the first step to making a lot more tricks. From there we develop strategies to handle them well. The guiding principle is often "set up long suits as a priority, before drawing trumps."