If you are going to pike or longspear(recommended) for pure support I HIGHLY recommend a 15/24 build. Put all your points into polewpf, GET WEAPON MASTER. IT MATTERS. Trust me on this, you want weapon master for the longspear. That extra bleh second will help you block overheads if you miss or hit the ground or do something stupid. Also, with about 140ish wpf you will hit almost as hard as 6 PS and 111 wpf anyways.
Now, lets keep this clear. With 5 powerstrike, YOU WILL glance...if you are not moving. Take advantage of the small point of the weapon and its slowness to maximize your speed bonus and aim for head or feet if they have crap armor. ALWAYS be moving, even if its a side to side disco. This will keep your opponent offguard, annoy him because he is most likely a str crutcher in comparison to you, and allow you a quick getaway or easy jumpstab. Just remember you have 8 ath and they most likely have 5, if even that. Abuse that difference and run circles around them.
I won't say using the longspear is easy, but it will take a VERY long time to get used to the weapon. You need to abuse your speed bonus as it is what will most make this weapon "OP" in the eyes of other. Abusing the acceleration from 8 ath is the difference between glancing on a plated dude, or killing him in about 2-4 hits from full hp.
In a team setting, pick someone and follow him. That is your anchor. You will also be helping him if you do something else, such as turning around and stabbing an enemy going for another teammate. Turn back around and support your anchor, if he dies, it is your fault in 99% of situations and you must replace him/her ASAP. Try and stay to the right of him is something i've heard helps, but I personally don't mind either side.
The better you get at supporting, the further away you can get from your anchor and the more teammates you can help at once. The more ath you have, obviously the faster you can move out to help a teammate and return before someone notices you. You should not be blocking, that is the purpose of the anchor, or human shield. If you do have to block, block once and run past the enemy. Jump and turn and stab them and return to your anchor. If you are alone, block until either the enemy gets bored or you see a chance to escape and outrun him.
Patience.