As a support main here are a few. And not just mentioning.
Xerath: You want to lane with someone such as Varus, Jinx, Cait, for their poke will not allow their ADC to farm. As for runes/materies. You may go 21/0/9 or 9/0/21 and for runes I usually run MR, AP and Scaling AP. You can get Movespeed with him. for this build you want 40 CDR. Depending on their comp you might want to get Void Staff and Liandry's. For Boots either Sorc or Swiftness.
In laning phase abuse your passive (mana regen) and spam as much as you can on the ADC but don't stand in their range. Xerath's Q is around 1400 units. One of the longest range skills and no ADC should be able to reach you. You are squishie stand behind your ADC and minions, if they engage Q their support (high CC) then slow their ADC and at that range you should be able to Q safety.
For teamfights, same as the lane actually, stand behind your team, ward around, and you will not initiate, but rather you need to spam your Q on their team. If you get Luden's Echo as well, you should deal a huge amount of damage. Remember to keep your E-R up. Mid game you should be able to cast your Q every 3 seconds. Your W and E should have around 5-7 secs.
Xerath will be extremely annoying and hard to deal will, except 4-5 man gank at early levels. This is why I get movespeedrunes.
Anivia:
With Anivia you should get movespeed runes and armor per level + MR per level and of course Magic Pen. For Masteries you can do 0/9/21, 9/0/21 or even 0/14/16. You should build RoA, get Liandry's as well. Zhonya's and probably Abyssal. Or do a troll thing. I build Zhonya's + Guardian Angel and bait the enemy team into killing me while my team is nearby waiting for their CD's. It's a troll bait and it works everytime.
For the ADC, you want someone with some sort of CC and escapes. I would say Lucian, Kalista and Graves will be perfect since they can hop over your wall.
For the laning phase you want to land your Q and then E as much as you can on the ADC. Make sure to ward since Anivia is slow. Sometimes I get teleport on her cause she is freaking too slow to get back in lane.
For teamfights, please as your team to take everyteam fight in to the jungle, that's where Anivia becomes a goddess.
Hope this helps.