Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
mastery tree: pretty self explanatory, increased xp useless endgame,clarity.. don't use it. in the offense ap/cd reduction and magic pen for harass.
Skill Sequence: I personally max crescendo>hymn>aria>song after the first point in aria of course. This also depends on your lane partner if you're putting pressure on them/ good harass use this if you're getting pushed maybe aria before hymn.i max song last since I get boots pretty early.
Runes: I like this rune build personally but cd reduction is also nice if your willing to spend the money also the hp quints are extremely recommended sona does heal but you need that extra 100hp buffer somtimes it can save you countless times.
Items: depending on who your lane partner is,mana manipulator might be a better start but regardless you want tears asap sona spams skills 1000 is fully reachable.majai's will depend on your confidence for getting 20 stacks late game.locket is the perfect item, but boots are very important for sona too so get those pertaining to your needs after tears then proceed to archangel.This 3 item build can sustain you the rest of the game mana wise you really shouldn't have much mana problems as long as your not just rolling your face. Now that your mana is good and you have boots to not get caught in a bad position sona is still very squishy and susceptible to the nuke, I like to start with soul shroud it seems perfect with its hp mana and cd reduction.Once you get to here you can decide which suits your needs better rylai's or zonyas either is a good choice and if youve made it this far your team is probably winning or turning things around lets face it.. all because of you =).
Summoner Spells: Flash and Clairvoyance
Flash is a must for sona, maybe youre trying to harass and find yourself in a omg 5 people are looking at me situation.. problem solved and you baited them.Running away and botts wont cut it? find a good juke wall and you're gone.
Clairvoyance.. some might be saying its useless but try it you'll like it.I cant play without it anymore after i tried it i feel ... blind o.O. but srs it is the ultimate support skill pop it where your intuition takes it and i can promise you it single handedly will change the tides of the game, and or let everyone know whose going where in the beginning of the game if popped right.
Tips: Positioning positioning positioning...you'll get a feel for it after a while like every champ but it almost seems most important to sona as your teams support you cant be getting ganked. dont be afraid to harass, surprisingly i think sona is one of the better harassers if played right with hymn and her passive chord make sure you use her passive on champions every time you have it... Hmm use crescendo wisely wether its to pick off a high dpser before a team fight or making their whole team dance while your team nukes they're faces off.
My build is not complete or absolute but i think this is a very good core build and this is my take on sona ty and GL =)