If you play Sona and you are ACTUALLY good at getting away from ganks, this build is for you. Unlike other guides I intentionally left parts of the skill chart and item build blank. The game environment changes around you, as should your build if you want to win.

Buy the boots of movement in the beginning then go top or bottom. Try very hard to survive until 700 gold for the Ionian Boots upgrade, as it's speed is necessary for survival, and the cool down reduction is great for Sona. Aim for last shots, and above all, aim for the long run. That means only being aggressive when your range will keep you safe, or you really think you can get a gank payout. As support you should allow your partner to get the kills, but if they are about to escape by all means blast the enemy. The 2 summoner spells Heal and Flash are obviously useful for ganking, but their primary purpose is to makeup for Sona's lack of survivability. Better get used to those hotkeys.

You should be attacking with basic attack most of the time. Sona has a big range, so keep your distance. You NEED be very conservative with your mana until level 3, at which point your heal is actually worthwhile. If you have a lot of mana, it's ok to use Hymn of Valor. At level 5 try to save up around 150 mana so when you level to 6 you can hopefully create a gank using your ult stun and either a heal or valor spell, hopefully both. Once you get the Tear of Goddess you can more liberties with your mana pool, but your mana pool won't be solid until you complete the Archangel's Staff. Part of Pro Sona is not dieing from every attempt at your life. If you have the patience, skill, and flash/heal cooldowns up, you should be safe until you build the Rabadon's Deathcap (yes start with the needlessly large rod). The problem with Sona I've noticed, is that once you have secure mana with the Archangel Staff, the scale of damage enemy champs do simply outdo any defense items you can muster at this point. So though you might help your survivability a little bit by getting something that helps your defense/health (like a Rylai's Scepter for example), you will be much better off increasing your AP at this point. Your attacks will be stronger, and your usefulness to your team with heals will improve (remember, Sona is a support, try and stand back).

Pro Tips:
When enemy champs are at their towers you can move in close enough to shoot them with Hymn of Valor safely. The time it takes for the spell to fly through the air acts as a delay on the turret's reaction. So you need to move in, shoot, then move back immediately after casting Valor to avoid a turret shot to the face. This quick in-cast-out action with Hymn of Valor is great for harassing Champs as well.

Your Song of Celerity active ability has an overlooked bonus that nearly every Sona vs X champion debate has left out (usually Soraka) that incredibly helps in Sona's pushing abilities. Go to the center of your minions and activate it. All of your minions should get a speed boost, which makes them setup on turrets/minions faster. This is a tremendous help while pushing (especially when pushing base turrets, having the minions there faster is useful).

Now this is where most guides inherently fail, because a guide for one situation does not necessarily work in all situations. Even the following are mere suggestions, that usually workout for me.

The Item Build:
If the game goes on long enough where you actually build Rylai's Scepter, you need to look at the makeup of the enemy champs.
- If you are taking a lot of magic damage, I recommend building an Abyssal Scepter
- If you are taking a lot of physical damage, I recommend building a Frozen Heart

Either way those 2 make good last items.

Abilities:
After level 6, your only set priorities:
1) Aria of Perseverance (heal)
2) Crescendo (ultimate, duh)

Now for Valor and Celerity auras, you need to look at your partner:
- If they are a strong carry, and can definitely pull off the damage to gank with heals, then level up Celerity first, as it will lead to even more ganks. Also make sure to use Celerity a lot in team fights, and end game, as it will lead to bigger pushes and less team deaths
- If they are are a support, tank, or a bad carry, you want to level up Valor first, as the extra damage is needed

Either way the item build works. If you play like a pro, this build will work great.