Leading
Every trick starts with a lead, and whoever leads sets the terms everyone else has to answer to. A good opening lead isn't about the single card you play: it's about which suit you force into the open.
Read the official rule on who leads and who wins a trick.
Three low Diamonds, more than anyone else can be holding. Lead into that suit and you're the one who decides how it plays out.
Lead your long suit
Lead from the suit where you hold the most cards. You wear the defenders down faster than they wear you down, and every card that falls tells you more about who's still holding what.
Leading a safe Ace
An Ace in a plain suit is the simplest safe lead there is: nothing outranks it, so it wins the trick the moment it hits the table. Cash it early, before the suit gets thin and the trick stops being yours to decide.
When nothing else fits
No long suit to lean on, no safe Ace to cash, nothing else the position calls for? Lead low. Giving away the least information and the fewest points is a perfectly good plan when you genuinely don't know what's best.