I am not a support main, but I am Gold V and support often with 
and 
. Support is becoming my 2nd role (after being my 3rd) since the mage changes.
First, I try to figure out if my adc is going to respond or follow up with any of my landed skill shots or attacks. If they aren't and just a "farmer" then I stop playing aggressive and focus on making sure they are protected, while also trying to auto attack the opposing ADC or support. If they follow up, I continue early harass but try to manage my mana in case the jungler comes.
I try to place a "ward line" and I move it up or back depending on how the team is doing. Essentially, the line is the entrance to our jungle at the start of the game by dragon and then it moves further back or forward depending on the state of the game. The ward line moves to the north side of the map as baron becomes more important. The ward line is critical for enemy positioning and protecting our jungle. In games, once your jungle is overrun by the enemy it will lead to tower dives and lost towers.
It is harder to carry a game as support. Most support mains are much better than their divisional placement. The problem is that their rank is largely determined by surrounding help. They can make it easier for their teammates to win the game, but they can't make them decide when to take important objectives or secure kills. If your adc is bad at making decisions misplays will happen a lot, and more misplays lead to greater likelihood of a loss.
I try to guide my teammates the best I can and make things "easy" for them. That is my job. Also, avoid dying. Low elo supports will sometimes die too often in fights to secure kills when it is unnecessary. What is interesting is that by playing I learned how to reduce my deaths. If you get touched you die, this champion helped me a lot with positioning.
I will say though, I feel like support is a very unrewarding position. The items aren't great, they are always levels behind, and they get very little glory if there is a win. The ADCs often insult supports if they mess up or when a mistake happens. I really think these are the main reasons why the position sees less play. The expectation is to play perfectly and enable your teammates to win, which doesn't always happen. I don't mind support, but once my ADC starts flinging insults at me I leave them.
. I play 
once in awhile but realize I am not too good at him so try to keep it to a minimum. Below are a few things I think is really important in playing support and will help you carry the game for your teams.
? A pull could win you the game if you catch an enemy carry late in the game but could also lose you the game if you grab a tank such as 
. Similar thing with 
and using it at the right time, warding well and clearing wards, can all help you win games.
