There are basically three ways to park your Ship at an Island or Outpost:
1.) using the Anchor (the "easy" way):
Releasing the Anchor and catching the handles before it drops all the way, then walking backwards to lower it to the last tip: This allows you do drop it almost instantly, giving you very high precision to park your ship where you want it.
While it is not recommended to park a Galleon using the Anchor, this method does work with both Galleons and Sloops.
2.) The Sails Method (experienced players): On a Galleon this requires coordination as the Helmsman should never leave the wheel during this maneuver, so the other crew members need to raise the sails in time.
Between one and two ship lengths worth of distance, rais all the sails all the way, your ship will come to a complete stop after aprox. 1.5 ship lengths. You can go off and do your voyage thing once all sails are up and the wheel is in neutral position.
If you raised the sails too early, you can drop one sail by 10% for 2-3 seconds to give you an additional push.
Works on Sloops but mostly useful on Galleons.
Benefit: Not dropping the Anchor allows you to move quickly in case of an attack!
3.) the Crash-method (sometimes none of the others are available :)
Just crash into where ever you need to stop, drop the Anchor, repair the holes and you're good to go.
Remember that the Anchor DOES NOT CONNECT while your ship is considered "beached"! It will connect once your ship has slit off whatever sand bank you beached it on.
Also note that while being beached the holes in your hull do not cause water to flow into your boat, but the Game still considers your ship "sinking" and after a certain time it WILL despawn, even when beached!
So repair all holes when you do this stunt!
[UPDATE]: Any ship will de-spawn after a few minutes when beached regardless of repairs if it is not able to slide back into deep water (e.g. when beached on a lagoon like Lagoon of Whispers).