Sona is one of the best supports in game, beside Janna. Sona has massive poke with her Hymn of Valor. This is my build for Sona. Dont judge me. Its my first guide =D.

Pros
*Pokeage
*Lane sustain
*Blue hair
*CC(Stun,slow)


Cons
*Squishy
*No Escape like Soraka, Janna can always tornado and shield. Soraka and Sona, However, Have no knock ups or shields.
*Slow movement speed, Which is why I take Mobility Boots

Greater Mark of Armor - I take these simply because Sona is squishy. Armor early game always helps reduce damage taken, Making it easier to stay in lane.

Greater Seal of Scaling Mana Regeneration - Mana Regen. Important on supports like Sona or Soraka. On sona you will constantly poke at people. Doing this will drain mana quickly. You will also be spamming heal if needed.

Greater Seal of Armor - More armor.

Greater Glyph of Magic Resist - A bit of mres wouldn't hurt =D.

Greater Quintessence of Gold - More gold = More wards.

These are just my choice of Runes. If you feel some may not suit you, By all means, Change them.

Q/ Hymn of Valor -Massive poke. Great damage, especially if you have the aura for it up. Max this 1st or consistantly with Aria of Perseverance

W/ Aria of Perseverance - Semi good heal. Short CD. Heal is good for its CD. Soraka's Astral Blessing, Heals twice as much, With a twice as long CD. Therefor, I prefer Sona over Soraka. Long CD's are something I can't stand. Max second.

E/ Song of Celerity - Rather useless for me. Since I never really use it. Only to slow or chase someone down. Max this last.

R/ Crescendo - Great for team fights and chasing someone. Just stun and might get a team ace. xD

]

I take Health Potion and Sight ward, along with Faerie Charm 1st because Fairy charm builds into Philosopher Stone.

I take the common gold per 5 items. Late game I build those up into Shurelya's Battlesong or Locket of the Iron Solari.

I build Archangel's Staff for mana per 5 and a bit of AP.

Will of the Ancients is for the AP Carry. Sona Is a support so, this item may help quite a bit.

Aegis of the Legion Always good for supports. It helps the squishy AD carry's like Caitlyn or Ezreal.

Mobility Boots Simply because Sona is SLOW. Very SLOW.
is another item you can use for supporting. Altho people say its useless. The mana per 5 aura can really help AD carry's like Sivir and Ezreal who tend to spam a lot. It also has cd reduction.

Zeke's Herald is also ideal for supports. It can help your AD carry in lane. It can solo be good in team fights,dragon or baron. It also gives hp to you. Which is a PLUS.

These are my top choices for summoner skills. Heal gives extra sustain in lane. Make sure to only use it when needed or it might go to waste. You can save your live or your fellow teammates. [[Flash is pretty much your only escape. Meaning..YOU NEED IT! If a support doesnt have flash..They might die because of no escape. Dont be that support!

Clairvoyance is also good. Only take it if you know when to use it.

Sona Is my favorite support. When supporting on Sona be sure you ward in the correct places! I start warding at level 3. 1st you ward in the river. I ward a little behind the bush, so we get a good view of when the jungler is comming. Then I ward the tri-bush in my teams jungle. You can also sneek and ward the other teams Blue or wolves. But, make sure you dont get caught! As long as you ward and becareful you should have no problem dominating your lane with the AD carry.

When im supporting with Sona, I hide in the bush located closest to the enemy turret, Then I will poke with my q and use my Power Chord when its activated. I actually 2 shot a vayne before. It was quite funny.

I hoped you liked my guide. Sorry if its not the best. It is my 1st! Please comment to see what I can change.