Nami Swaaaaaaan patch 6.18 (Pros dont know how to nami...luckily :D)

Matchups
I tried rating the match-ups as if all bot players had the same skill. Also i only rate how easy or hard is to WIN the lane. By winning i mean having a significant gold or lvl difference, or forcing jungler/mid/top to help the enemy laners.

Pros

• Aoe stun + knocup
• Hard cc + buffs + heal
• Can disengage
• Wins early trades
  
• High killing potential early game.

Cons

• Wasting Q is extremely punishing
• It takes skill to play nami
• Runs out of mana if skills are not used wisely
• It takes time to understand nami's full potential and that requires pushing to the limit and making mistakes.
  
• Nami's initiation is not optimal, and can cost you the game

Your role...
    Some people believe that supporting is all about protecting your adc-team, warding and CCing enemies.......well...i kind of disagree...For me support position is mostly about making things happen, making plays, creating for your team. Its like the Point Guard position in Basketball. In the following parahraphs ill try to break down each of your responsibilities, focusing on playmaking!! 

• Warding - Map control. You can only place 3 greens-1 pink. Thats all. Convince your teamates to buy wards!! I am not going to teach you where to place wards. Thats another guide. All i can tell you is to always have a ward on dragon and if you can on tribush. Just do this and your lane will be safer. Make sure to watch the minimap whenever you can! Make it a habbit of yours to watch the minimap. Search for the jungler first, then check if lanes are pushed and enemies miss. A pushed lane to your mid touret and mid missing is a possible danger. In late game you are the one to place the smart wards...Deep wards in their jungle, mid entrance wards...etc. In my opinion warding baron should not be supports responsibility. Remember, convincing your teamates to buy wards and lens is actually more important than placing your 4 wards in the map! And significantly harder to achieve.

• Potecting. You are the player with the most cc in your team. You must try to stop a running udir going for your adc, or heal a teammate dying from ignite. Should you stay behind your adc to do all these??? NOOOOOO. In early game if your adc is engaged on, you must Q enemy adc, self cast E and slow both supp and adc, or even the jungler :P. Use W first to give your adc a boost, then self cast E and use Q while you autoatck, or AA with E first, for increasing the succes rate of Q. In early game you should be able to turn any aggresive move of the enemy team into your advantage. Never be affraid, be in front of your adc, take some damage for him. Never run back if your adc is being hit. AA the shit out of everyone trying to get to your adc. Your aa mechanics should be better than your ADC's! Always orb walk (cancel animation of aa and skills). Offense is the best defence. In late game you must try to  Q the enemy apc -adc + R. Then you must protect your adc... If you cc enemy carrys but your adc dies before you start to peel for him...its his fault!!! 

• Playmaking!!! This is it, this is nami swaaaan, this is all the fun on playing support!! If you miss this part, playing support will always be lame, its going to be this last pick (pick order) that will make you miserable...You are a playmaker, you are Magic Johnson of LoL or better John Stockton of LoL, your adc is Malone. Dont expect your adc to be Jordan. He will never be... Too many references, why not? Basketball and LoL have a lot of things on common!
  

1. Early-mid game. Laning phase is all about TRADING. Search for TRADES. You must always AA every opponent thats out of position, while he is going for a Last hit, for a trade, or for a ward. If you see the oppening in 1 of these situations use Q, dont hesitate. Never use Q if you dont feel its going ro land...Its like shooting a 3-pointer in Basketball or a penalty kick, you must picture it landing before you even cast it. Your adc should always follow you. If he doesnt, you can still make a clean trade, Q+E +AA+W+AA. If your adc is bad and doesnt follow, then search for a Q when your adc is close, to "force" him trade.That means that you will hold yourself and w8 for the perfect moment. In lower ELO you can start a trade with E first then Q, because ppl tend to make a lot more mistakes and wrong steps. In higher elo you should start with a  Q, or E at your adc that has a better position or a gap closer. A succesfull Q is always the best situation cause it means that you will win the trade. If enemies are Full hp, dont go all in, the damage is not enough for 100-0. You should first win a small trade. If you cant take the early advantage in lane...can mean 3 things...1. you are being passive, 2. Enemies have a lot better mechanics. 3 you made mistakes. Always be aggresive dodge skillshots and keep the preasure going. Never stay back after a won trade. Always be the annoying person you always hate to deal with.
2. Late game. This is tricky. You are NOT the initiator of your team. You are not leona. I've seen a handfull of LCS teams drop a game because they tried to initiate with nami. You need someone else to start something small and then unleash your power. Chaining CC after an initiaton is Nami's best. BUT there are ways to initiate!! Clear vision and make a trap. Bait enemies on a pink ward, or bait by pretending to be out of position. You can use ulti from a bush, or behind a wall while you click shurelias. Your opponents will have less time to react. AND if you feel GOOD, flash+ Q at the apc or ADC if your team is ready to kill it. This is the ultimate challenge for a nami player. (like Knife in LEON the proffesional) You need a ton of confidence and a pair of Big Balls to land this small bubble :P. Trust me, nothing feels better than catching 2 carrys with a flash+Q on minute 45! Never be afraid to follow a good CC with your ulti. You must do this fast cause the wave travels very slowly.

•           Disengaging. Nami is propably the best support for disengaging. Maybe Janna and Zyra are equal. If they run on your team just use R and its over...they will abort! Q alone is also that good. Q their initiator, they abort, then your team repositions... You can also speed up your teamate who's out of position.                           
•    Roaming. Its the new season 5 meta. Roaming is when you leave your lane to gank or assist a gank somewhere else. There are some things you must consider before that. 1 Your adc must be safe (either he recalled or 1 v 1 on bot or clearing jungle camps until the minion wave arives, or with you :P. 2 You have enough vision both for your ADC safety, and your safety (wards on tribrush, enemy jungle entrance, river entrance from mid). 3 Make sure you wont be seen, there are a couple of ways to do that i) vision clearance ii) the person you will gank is absorbed in trading-lasthiting (tunel vision). 4 Check if your laner has lvl 6, you dont want to share his exp and delay his spike. 5 Make sure your teammate saw you and understood your intentions (you dont want to engage solo and die). 7 In general make sure you dont make anyone angry from your team by "breaking" the laning phase rules. Seriusly if you fail people get angry more than usual and its fact, its not their faul! BUT if we succed its you who carried them!

• Lane momentum-setting last hits. You can always AA minions, either to stop the lane from being pushed, or for pushing the lane. If you see the enemy adc-supp pushing the lane, start autoattacking minions. If you got a kill and you want to recall, use Q on minions and aa like crazy. You can also set last hits. This is very important and only high elo supports do it consistnently and effectively. This is more essential while under your tower. Try to learn when a minion needs an additional AA for your adc to last hit it. Or when the lane is not under your tower, use AA to set a last hit. This gives time to your adc to harash, insetad of w8ing for the minion to go low enough for him to last hit.

•             Timers announcer. Objectives timers. This should be mostly your junglers job, because he is always involved at taking and contesting all 4 buffs and he is most of the times the one to kill the dragon. If you see a timer that he doesnt, f.e. a sneaky dragon or a buff steal, then call it. write in chat. (OB-TB-OR-TR) + respawn time. OB = our blue...etc
  

           Ward timers. In s3 you could keep easier track of wards since the vast majority of wards lasted 3min. Now its harder but in high elo it is good to write the time of wards that are being placed. f.e. You see a green ward placed on tribush. You can ping and just write warded, or Ward or Wrd or w/e :P The ward will be off 3 minutes later. You can also help your jungler by giving him the clear path for a gank at bot. f.e Tri clear, lane clear etc... 

•  Making the calls. In many pro teams its either the support or the jungler to make the calls early in the game. If you feel like a leader, if you strongly feel your calls are correct, and if you have it in you to lead, make the calls! You should never look bossy because lol players, are narrow minded :P
  

I am mad4u, call me mad  EUW (D5). CaLL me MaD eune, season3/4/5/6, all diamonds.  I started playing ranked in season 3 ( the week got released ) I started at silver 4, being a total noob and got to d5, just 1 week before the real season 3 ended. I had ~ 400 nami games, with over 60% win ratio

            K      D       A 
 KDA   1,5   3,6   15,5   thats 4.8   KDA ratio.  season 3  Diamond 3

Western supports have not practiced enough with nami, in different game scenarios, to comprehend when to do what.  Ill list some mistakes i ve seen.