Shadow Shaman is a fairly straightforward support hero, with just about everything you could dream for in terms of abilities. The highest damage level one nuke in the game, an ult which is multipurpose in its ability to change the dynamics of fight positioning and push down buildings hard and fast, and his shackles and hex which, combined, allow Shaman to lock down an opponent for a total of 8.5 seconds when fully levelled, 11.5 if you get the shackles talent. By that time your hex will have come off of cooldown which means you can theoretically lock down an opponent for perpetuity.

In the laning phase, think of your ability build in terms of whether your carry has more disable or right click damage. If you're playing with a Gyrocopter or an Anti-Mage, two heroes who have a fair deal of right click but little to no disable, you need to be putting your first 5 levels into hex and shackles. If you're playing with a Tiny or Tusk, heroes that have strong disables in the early game, max out shackles and ether shock first instead to compensate. It really is that simple.

Later on in the game, think of your play as being dictated around your ultimate. If mass serpent wards are up, you should be looking to push or fight with your team. When they're down, stack camps, place wards, and be reactive to the enemy team's positions around the map. Basically just babysit your carry and make sure they're getting sufficiently fat. If you can apply this correctly and the early game isnt a complete trainwreck then you can expect to have all the opponent's outer towers down by somewhere around 25 minutes and then, if that has been done properly, the gold and xp advantage should be stacked enough that you can consider highground.