Potential tricks are the ones you can get to only after you make a play that transforms lower cards into winning cards. If you do nothing, someone's lower cards will assume winning rank by force as the play progresses. If you play your cards skillfully, more of your lower cards than those of the other side will eventually win tricks.
With a few advanced exceptions, the correct of order of play is potential tricks first, ready tricks last. Most new players make the mistake of playing off their ready tricks, for fear that they will get away. Don't let fear guide your play. Caution yes, fear no.
There are four ways to convert potential tricks to ready tricks: