Coincidence is a useful thing. In real life it would look weird if you just happened to bump into your long lost twin brother or mortal enemy while out hunting deer in the King's forest, but in fiction (or games) this sort of thing happens all the time. So don't be afraid to play up coincidences and make them critical elements in your ongoing plots and campaigns.

And if the players ever get suspicious that there are way too many coincidences to just be random...

Maybe they're right. That should keep them up at nights for a long time.

Transcript

{The Rebel hangar}
Luke: Hey, Chewie.
Chewbacca: Good to see you ship-shape and primed for bally, Luke.
Luke: Han, you better prepare your guns.
Chewbacca: Actually, the guns are in tip-top working order.
Luke: Good. The base is going to be attacked any minute.
Han: Don't be ridiculous, kid.
Han: In fact, we don't need to evacuate. The Empire'll probably assume their probe droid self-destructed. It's a pretty boring planet to be exploring.
Han: Princess is over reacting. As usual.
Luke: She has the right idea in this case. We need to get away.
Han: You're paranoid. As usual. We're obviously not going to be attacked!
General Rieekan: Imperial star destroyers have just emerged from hyperspace.
Han: Coincidence!