Tips to Use Kunkka (Dota2)

• Tidebringer is your signature ability, and should usually be trained early and maxed out first. Notable exceptions would be when having a stun to chain would be advantageous for early kills or you need a mechanism to prevent escape heroes from running away.

• Use Torrent to initiate battles and disable opponents.

• Try to get raw damage to maximize your Tidebringer damage.

• X Marks the Spot works well with Torrent to ensure you a hit. Leaving X at level 2 allows you to immediately cast Torrent after X because both skills have a delay of 2 seconds. Consider if the extra range on higher X levels is needed.

• Ghost Ship delays half of the damage dealt to allies, making it great for short team battles.

• Train Torrent first if you're going for First Blood, otherwise, train Tidebringer.

• Try dual laning with heroes such as Crystal Maiden, Shadow Shaman, Shadow Demon, Bane, or Vengeful Spirit. Their disables will help you land your Torrents.

• Use a high leveled X Marks the Spot on enemies who are trying to flee using a Town Portal Scroll and they will be brought back to the X no matter how far they've gone!

• The classical combo should be: Torrent and then Ghost Ship, but you can add X Marks the Spot before them if you are targeting a single unit.

• During team fights, either initiate with your combo when the enemies get clumped together, or wait until the battle starts and use it when they get clumped.

• You can use X Marks the Spot and a scroll of teleportation to go back to your base, refill your bottle, and go back to your previous location.

• Ghost Ship will always appear a specific distance behind Kunkka and end a specific distance from Kunkka(The only exception being if Kunkka is facing away from the edge of the map, but the ship will still travel the fixed distance infront of him). The distance at which the boat appears and hits can be seen by mousing over the ability and noting the radius circle behind and infront of Kunkka. Practising memorising the distance the ship travels in a practise game with cheats and wtf mode on can go a long way to pulling this wonderful ultimate off successfully.

• Another method to pulling off successful ultimates is to always set the target point for Ghost Ship to anywhere out of Kunkka's range. That way the end point and radius circle will always be placed where you clicked the target. 

source: http://dota2.gamepedia.com/Kunkka