Sona can be an extremely oppressive presence in lane due to her range and poke damage. Unlike 5s, her poke does not fall off drastically, so she has a consistent damage output, as well as sustain from her W. A mix of AP and AD allows painful Q's while buffing her power chords, and allowing for higher damage while she is waiting on cooldowns. Her Ult is a hard cc that allows her to set up plays for an easy ace.

Pros: High Poke/Damage Hard CC Sustain Can help support teammates if they fall behind Have to use Power Chord well Cons: Squishy Low mobility outside of her E Somewhat reliant on cds

Sona's Passive is Power Chord. After casting 3 spells, her next AA will be buffed with an effect and do extra damage. Blue is damage, Green is damage reduction on an enemy, and E is a slow.

Her Q is a poke. Press it and target to two nearest enemies, prioritizing champions. If allies step in the blue aura around her, their next AA will gain extra damage. Sona's next AA after casting Q is also buffed.
Her W is a heal. It heals the two nearest OR lowest hp allies. If allies step in the the green aura, they gain a shield.
Her E is a MS boost, and any allies that join her in the purple aura also gain MS.

The trick to playing Sona well is knowing which power chord to use and when. A good rule of thumb is:
Power Chord-Q is when you want more damage poking
Power Chord-W is like a mini exhaust: use it when you or or adc are taking more damage than you would like AND you can't kill them.
Power Chord-E is a slow, so use when your laners overextend so you can keep them from escaping, proc your true damage rune, and secure a kill. Alternatively, use if someone is chasing you to make a clean getaway.

Basic Combos:
AA-Q-AA
Your Q resets your AA timer so weave in autos when possible, but don't waste a power chord. This combo lets you do the most damage in the shortest amount of time, with a free regular auto, Q damage, and empowered auto( not powerchord).

AA-PWRC-AA
Same as above, just with the effects of each spell.

Flash-Ulti
A Good way to secure kills by providing some hard cc to the opponents face, and letting your teammates ********.

Due to the new runes, Sona is an extremely hard to kill, uber damage dealer if played correctly. The amount of damage she can do with her Q-Power chord combo is insane, and her slow, power chord E, can trigger the cheap shot mastery allowing her to do some true damage.

Aery applies to allies when using both W and E, as well as dealing extra damage on your Q poke, so it is the best choice here. Next I go ultimate hat so you have hard cc on a lower cd, which is useful for peeling and setting up plays. Finally take Absolute Focus so your pokes are even stronger, and gathering storm for some solid ap to boost your damage and healing.

In the Domination tree, I take cheap shot for the true damage proc on my ult and slow, and zombie ward for vision control.

Alternative choices:
You could go with Manaflow band, which eliminates the need for a Tear of the Goddess, in exchange for your ult being on a higher cd. You could also go Taste of Blood for extra sustain in lane, but i feel that the true damage proc on your ult and slow is more valuable in team fights and lategame.

In lane Sona's main job is to poke the enemy adc and support, while keeping vision control and throwing a heal to your adc as needed. A common mistake is to spam heal so often you go out of mana. You are not a heal-bot, so be careful not to go oom. Sona is mana thirsty before her tear, so use your spells carefully until then.

At 6, as long as your adc is comfortable, a good ulti can secure a double kill if you go all in. Get picks and kills from there. If you see an opportunity to roam and get a kill mid or top, ping your laner and feel free to go, but do not stay away too long.

Finally, with the Frost Queen adding the bandit passive from S7, make sure to AA the enemy laners, even if your spells are down for the free gold.

In teamfights, your utility comes from your damage and ulti. Start a fight with your ult and powerchord Q, heal as needed, and chase down stragglers with powerchord E. If the fight goes bad, E with your team for the MS boost, while healing them up, and poking your enemy on the way back to base.

Sona does well with ADCs that can be more aggressive early game. While that is very much a personal preference playstyle, some ADC champions do not work well with her in lane.
Good Synergy: Champions that thrive on poking, have some sustained damage, being aggressive, and going for kills. AD carries that can afford to take a few more trades in the beginning, or that are paired with crowd control. Examples would be: Jinx, Vayne, Kog'Maw, Miss Fortune, Xayah, Sivir, Draven, or Kalista.
Poor Synergy: Champions that have little sustained damage, are squishier than usual, have little poke, or are just particularly passive laners. Examples would be: Jhin, Caitlyn, Ashe, Kindred, Quinn, Varus, or Graves.

Now that my guide has been updated for S8, I thank you all for reading and wish you good luck on the Rift.

This guide has now been updated to S8. Former masteries were 12-18-0 with thunderlords decree. The build and playstyle is largely the same, though it now enables you to be a tad more aggressive.