It's easy enough to take tricks with aces and kings but there just aren't enough of them to go around! We need to establish extra tricks.
Three common techniques used to get extra tricks are suit establishment, finessing and ruffing.
Suit establishment is simply winning tricks from yout long suits.
How can you win tricks with those little cards? The concept is pretty simple. If you're the only one with cards left in that suit then all your cards are winners. Your job is to find opportunities to make that happen.
Look for the suit that you and partner have most of between the two hands because that's the suit your opponents have least of. Then keep on playing that suit. If you keep playing your long suit then your opponents will run out of them.
With a finesse you're trying to win a trick even though the opponents have a higher card in the suit. You're trying to win extra tricks from middle cards, Queens and Jacks.
Ruffing means playing a trump when another suit was led. That's how you score extra tricks from trumps.