Gonna go over some of the lane match ups you'll see.
Alister vs Leona is a weird lane. You both have gap closers with follow up CC that you use afterwards. Basically if you go in their Alister will do one of three things. Follow up on Your ADC. Knock you away. Or try and knock you further in (Especially if you are near their turret).
Alister has sustain in lane so if you drag things out you're going to lose. However, between your damage and your passive as long as your ADCs aren't too mismatched a Leona/ADC can very much beat an Alister/ADC. Especially post 6 where you get more CC and he just becomes tanky.
So either play hyper aggressive or hyper passive into hyper aggressive when an opportunity arises.
Another weird lane. Pre W do NOT get gripped. Post W it depends. If blitz wastes his grab on you with their ADC in range of your e and your ADC ready to follow up you can easily win the fight.
Respect his grip early and make sure not to get gripped under their turret late. Make sure your ADC plays near the minions for protection. If you play this lane smart it's a pretty easy lane for you.
Honestly this lane comes down a lot to player skill. Janna has good poke and pretty good CC. She's fast passively and has good disengage.
However, if you land your Zeniths and avoid her poke you'll probably win straight up exchanges. Janna is also pretty squishy and fair game to engage on with say, an exhaust on the ADC to shut their damage down.
Don't let her auto attack her for free and be in a position to turn on her if the chance arises.
A good Leona will beat a bad Lulu. A good Lulu will Crush a bad Leona. Depending on skill it could go either way in a close match up and this is going to come down to your ADCs skill a lot as well.
Lulu has high mobility and high poke. If a Leona lets Lulu whittle her down she's dead in the water. However Lulu is still squishy and can definitely be a target for a Leona all-in.
Play this like you would with Janna only with more respect for Lulu's poke than you would give Janna and less worry about disengages.
Dodge her skill shots and all in whoever you want. Lux shouldn't beat you unless she's landing her spells, specifically her binding. So dodge them. In this lane I might consider going boots ward pot at the start.
In a full on engage you should beat a Nami lane as long as you're at least level 3. What you have to look out for is her ranged poke and her synergy with jungle ganks. It's similar to a lux lane only without the constant danger of your ADC getting gibbed and having to deal with actual sustain instead.
Dodge spears. All in ADC. Collect kills. Nidalee has no real way to stop this chain of events.
This is a rough lane. Nunu is tanky, he buffs his ADC and he slows your ADC down. You don't want to all-in him like you might do to the squishy supports.
Don't let him chuck free snowballs at you or your ADC. Use the brush effectively and simply q him if he comes in for a snowball. Get your ADC to pop it with an auto and back off again after the stun is over. Nunu is tanky and has sustain but unless he's auto attacking he can't keep up BB, snowballs and consumes for long or he'll go oom.
If you get a good hard engage on the ADC go for it, nunu can slow down your ADC but between his abilities, your damage, and your passive you can still very much get a kill.
If you are against a Sona all I have to say is this:
Sona is squishy, incredibly squishy. She lacks CC outside her ult. If you all in her, she will die. Exhaust the ADC to stop their damage and switch once the muse is dead.
Soraka lanes are pretty much going to depend on how you handle her poke and who gets ahead early on.
Between the armor buff on her heal and the magic resist from her passive, soraka can make hard engages on her ADC be fairly lacklaster. And if you're already behind you'll have issues turning landed zeniths into kills.
However, if you can get ahead in the lane early on by denying her poke on you with proper positioning and working with your jungler you can snowball the lane as Soraka doesn't really have the tools to stop your CC and damage if you pop your q and w before using your zenith to engage.
One of Leona's hardest lanes. He has a ranged stun to throw down on your ADC when you go in and an armor shred to compete with your sunlight damage. Passive armor to be tanky and possibly most problematically he has a heal and therefore sustain.
The only thing you can really do is abuse his mana. Taric mana costs are high. If you can force him to heal over and over without taking too much damage you can force him out of lane or force him to auto attack for his mana, pushing his lane and leaving him open to ganks.
Laning against Thresh is like laning against a Blitz. Don't get hooked in your early levels where you don't have the tankiness from your W and make sure to take the hooks for your ADC afterwards, although nobody getting gripped at all is preferable in a lot of circumstances. However,as long as he grips you, your ADC is close enough to engage and his jungler isn't nearby you should come out ahead in a fight if you can get on their ADC after he pulls you in.
This is going to come down essentially to skill. You can kill a Zyra, she's pretty squishy. However Zyra support does very high damage. Positioning and landing her spells will be what this match up comes down to.
Don't let her land Es for free. If she does, especially with seeds down, pop your w to reduce the damage that's no doubt coming.
Stay as high health as you can till you can engage her but in particular with Zyra it's going to be more advantageous to go for the ADC than her if you want to get away clean because of her passive. Zyra is still quite killable but the opportunity cost of the kill may very well be too high.
After her nerf this is a much easier match up but you still need to be careful. If you do go for the zyra first and kill her, don't let you and your ADC be in a line to both be hit by the passive.
Easy. No dashes, flashes, tumbles, or massive nets to send you flying away. Land your Zenith and go to town.
Cait can be annoying with her high range and net get away but she also doesn't have the umph a lot of other ADCs have to force you off her support. If the support is tanky just play for farm, Cait's late game is still weak. If she uses her abilities offensively, especially her net, you can always go in afterwards, turning on her.
Corki is a pain in the ass. His one real weakness is mana. Unless their lane has really high sustain like a Soraka, play on forcing valk. It will drain his mana pool and either give you an opportunity to fight him without his escape or force him out of lane.
Respect his damage though, especially in lane.
Don't fight this guy at level 1. Just don't. Hell, don't fight this guy at level 2. Draven does scary damage early game. Wait for level 3 and a clean engage followed by an exhaust. He has nothing to widen gaps but a small sprint so no worries there.
Honestly unless you trust your ADC I would just wait for a gank. Draven is very gankable and Leona is a very good support to gank for because of her CC.
A good EZ is going to shift any Zenith you land and play out of range while it's on CD. It sucks but it happens. Just be ready to stun him if he shifts offensively and try to dodge his qs. If you can force his shift enough he'll go oom like Corki but it's a lot harder.
If his support is squishy feel free to go for the support while exhausting the EZ.
EZ is not a great ADC to play Leona against. If you are picking after an EZ pick I wouldn't really suggest Leona.
Graves is like Cait only instead of poke you have to be aware of his raw damage. Unless you have exhaust I wouldn't suggest focusing his support but landing Zeniths into qs isn't nearly as hard as on EZ.
Feel free to go in on him as long as you have respectable health levels and w up. But make sure that your ADC is following or you're screwed with graves damage.
Kill him. He does a lot of damage but you have a lot of resistances with your w. Just be careful if he's running cleanse and turns hard on you.
Lucian has fairly good damage in lane and a dash. However, his dash is on a fairly sizable cooldown early on. His level 6 is also pretty weak compared to many other ADCs.
Honestly this lane is pretty vanilla. As normal avoid poke until you see your level 3 spike in power. If your ADC can go in with you at any point after that feel free to engage, especially at level 6.
MF is like the other champions with no dash in that she can't just dodge your Zenith. However with her passive she is very fast.
Co-ordinate with your adc to get in an AA to strip her passive then go for the Zenith when she's back to normal speed.
Quinn isn't that bad of a champion to have to handle in lane as Leona. Her disengage on her ultimate can be frustrating but as long as you and your laning partner start the fight with her low enough or do enough damage during your CC you shouldn't have any trouble killing her. And if she engages with it just make sure to get on her ASAP.
One thing to be careful of is her using Vault on your ADC when you go in to Zenith, getting poke And dodging your blade. As long as you avoid that exchange you should be fine.
You can win but it won't be easy and you probably just won't win. If you land your Zenith she just shields herself and stops your q. If you don't q and wait it out she's just smashing you in the face with her support.
If she plays stupidly and shields before you go in you can easily get a kill but really, why would she do that?
Trist is an interesting match up with against Leona. On one hand she has a massive leap to avoid your skillshots or disengage with but generally it's also a large part of Trist's early game burst and having to leap away instead of letting her leap IN keeps her very defensive. Trist also excels at handling high sustain lanes which doesn't really affect Leona.
Make sure to pay attention when her and her support seem to be closing in on your ADC so you can lock her up after she jumps and you should be fine, her all-in isn't very effective on you with your early game MR from W.
Pretty much like Ashe or Kog. No way to open gaps and therefore easy prey. Just be careful of his burst. Try to avoid poke until you can full on engage. Between ignite, his passive and expunge he can easily kill you if you go in low.
This lane is a lot like the Ashe, Twitch and Kog lane. He has no dash or tumble or flash. Go in on him with your ADC alongside you and you should kill him.
Vayne is a weird lane. On one hand her silver bolt mechanics counter the crap out of you. % health true damage screws your high health pool and high resistances. On the other hand, vayne is squishy as hell. Land your full combo and she's probably dead unless she flashes away.
Just make sure to respect her damage, if you aren't careful and get condemned into a wall you could very easily go down.