Disclaimer: You can take my advice with a grain of salt as I'm also in Silver, and not a support main, but I thought I'd post this anyway in the hope that it helps.
I haven't really ended up playing support a lot in my ranked games (I main top), but of the ones I have played as support and done well with, I did a few specific things. One of these is if I do end up as support, I'll pick a support that can solo carry the lane if I get ahead, such as 
. All 4 of these supports can carry the lane if you get a gold lead over the enemy bot lane. What I usually do is build either 
or 
+ 
(if you don't want to lose the ghost active) and an AP tank type of build afterwards (or straight AP if you have a tank top/jg).
Also, if you get support and notice that your ADC is absolutely clueless about positioning/CSing/dodging skillshots etc. and goes 1-7-2 in lane, then during teamfights I'll shift my focus from peeling for them to peeling for my teammates who actually have shown that they have some basic game knowledge and could potentially carry with some help. If you find yourself in the position of "my ADC is garbage, and I don't think I can solo carry this game" pay attention during teamfights and see who on your team is making good plays and leading the team, then be their support instead of your ADC who is feeding.
At lower elos, I notice that a lot of the time supports will hold out on their abilities in favor of letting their ADC take the kill. While this is fine if your ADC is in no danger of dying, if it's a closer fight don't be afraid to use your abilities if it could save the ADC from dying or prevent the enemy from getting away with 10 HP. Taking the kill from your ADC is always worth them not dying or letting the enemy escape (even if they may flame you for it, in which case just mute them).
If you do manage to kill the enemy botlane and your jungler is nearby, ping dragon or the turret for assistance and try to snowball that good play even more. Don't simply get a double kill bot and immediately base unless you are both low and don't see the enemy jungler/midlaner on the minimap. Additionally, if you are winning botlane try to avoid keeping your lead in botlane only. When possible, try to roam to mid or even toplane and get that lane ahead also. While a good botlane can certainly carry a game, it makes it much easier if you can help your mid and top catch up to their laners or extend their lead.
Since you aren't actively trying to CS as support, you have a lot more time to watch the map. You can use this to your advantage by being the "global eye" and pinging warnings around the map where needed. See the enemy jungler taking top scuttle with full HP, but your top is still pushing with half HP? Ping a warning symbol at scuttle and type "jg topside" so they can back off in time. Is your midlaner under turret with 1/4 HP and no summs, and then you see their jungler go into the brush between blue buff and midlane? Use a warning ping on that bush and say "jg in bush" so they can back before the dive comes.
If all else fails, try to find an ADC main (of the non-toxic variety) near your skill level you can duo with. Play several normal games with them, then see how they play and try to get used to it. If you become confident in your combined skills and playstyles, it shouldn't be too hard to carry. You can even use a free VoIP service such as Skype or Discord to enhance your communication even more.
Good luck!
Edit: Feel free to chime in if you think any of my advice is wrong, as I mentioned above I don't main support and am Silver currently.
and peel like an irish potatoe farmer for whoever is killing the enemies of your team.
