We all know how to play league of legends, we wouldn't be on here if we didn't, so I wont waste your time with simplistic mechanics. As a support, the beginning of your match up until you destroy your lanes tower is focused on your ADC. If your ADC doesn't like what you're doing, stop it. If they tell you to do something, do it. If you think that you can be all smart and swap lanes you just might want to ask your ADC first. A nice thing to do is ask your ADC about how they will be playing before the game starts, things like if they want you to attack minions, if they want you to ward bushes or not, etc. It's always nice to do, and tips the game oh-so slightly in your favor. You also should communicate with your ADC. I know how simple it sounds, but it really is helpful if you understand that you and your ADC are central to each other. If either of you play in a lack-luster fashion, both of you will suffer. And as a duo, you're going to need to communicate. Find time to do it, as it's helpful. While your at base healing, while your walking to the tower, and any other situation where you can fit it in. Good communication is very important. Sometimes your ADC is just an idiot, and you may find yourself asking what you can do. You don't always have to stick with them, in my opinion. If they're stuck on pushing bottom lane while the inhibitors are about to get destroyed, it's possible that they might not be doing the right thing, and you should go help the rest of the team defend.

Don't overextend. Even if they aren't shown readily, there are some lines you should not pass as a support. Unless you are absolutely CERTAIN it is a good play, do not run far past your ADC. Don't ever unless you are aware that nobody could even POSSIBLY gank you go past the river while your ADC is dead. It may seem like a good idea, but it really isn't. If you aren't getting the last hits on minions, letting your ADC have them instead, you aren't getting as much gold, therefore not getting as many items. You are also likely not the same level as your ADC, which is usually above your level. The people ganking you do not have either of these disadvantages, and are likely higher leveled than you. Another nice fact to remember is to keep an eye on your ADC's health, and look at the health of those who you are preparing to support. Once you've destroyed a tower in bot lane, you can rotate, but you should keep an eye on the health of those you are going to help. If they're low, unless you have a healing ability, which likely can't do enough to save them anyway, you might not want to try to help them win against that champion who's bugging them. You should also try to help in teamfights, but keep the previous tip in mind, as it helps for this also.

Remember to ward. It's central to your survival. Control wards are something you should almost always get when you can, and place carefully as often as possible. You should so the same with regular wards, at least the careful placing as often as possible part. The bushes/alcoves are usually a good place to start, but you should adapt to your enemies tactics and also how your ADC places their wards. If you don't have any wards but really think that an area is unwarded and really needs to be, let other know. If you can, try to know where the enemy jungler is at least most of the time so you can warn of ganks. If possible also warn others on the map of incoming danger.

Know your towers. You should try to know their radius, how fast they'll kill you, and how fast they'll kill your ADC. They deal damage FAST. It might seem simple, but you should try not to let the tower target your ADC. Don't kill yourself over it, as they probably will get out of their after you tank a hit, but it's more important to just not let yourself get into that position in the first place. You will also need to know how to play around towers. Unless you have a long range, you will likely not be able to retaliate in kind when you get attacked from a tower. Just because your ADC is poking doesn't mean you should follow him right near the tower with people in it unless you also have a plan to get out.

Personally, I love the new alcoves. Nobody ever thinks to check there, for some reason. Now that I think of it, even though this is a support guide, they'd be pretty handy as a jungler to make some power plays. Grabbing champions can put them to great use if they're smart enough, grabbing champions into the not-often visited alcoves and beating them up with an ally. While sometimes the bushes are better for this, those are what people think to ward, and alcoves are not what they usually expect.