Maybe don't have too many ask. With all progamer from High Elo, Alistar is a well support.
WHY YOU STILL IN HELL ELO? Maybe Alistar'll help you out @@

Hi, again with PTP. I was a main of support. Long time ago (patch 7.9), i'm boring and try this Alistar champ. I thing it just a norman game to check what updated in this patch from Riot. Well, i got good game! xD
Then i like Alistar, then asking me "why i still in Hell Elo? maybe Alistar help me." And yes, now i'm Diamond II.
I thing this guild will help all who read to go out from Hell Elo and be a pro

So, here's the pros and cons at Alistar

Pros:
Good recovering HP for your team with Passive from any Harassing Enemy
Strong at all time in the game
Very high mineral health and sustainability
Style aggressive play suitable for positive ADCs
Can create a surprise in the fighting
Have many CC and R to put of enemies CC

Cons:
Damage's to weak (but not need damage at Support)
Slow moving without boot (i mean in started game)

So for the runes... there are a lot of choices but these are the most straightforward for the laning phase and can help stomp early.

I will explain them as simply as i can. You go for 0/12/18. For your keystone mastery, you can go with a lot of options depending on how you play but for me i wanted tank sustain:
+ I used Courage of the Colossus. It will gine you a shield (about 200 - 700) when you used any skill with Hard CC, and alistar have 3 skill with Hard CC