I agree with what Oreowannabe said. Pick a champion in any role and really master them, it helps to go into ranked playing a champion you know from every direction other than picking a counter pick and completely losing since you have no idea what do do with them. What I learned from my time in Bronze(and I dipped as low as bronze IV) back in season 3 is that being kind is key. I know there are times that people are completely unbearable but you have to deal with it, act in a kind manner, and try to communicate as best as you can. Pinging, warding, and giving players positive feedback or raising their morale can go a long way. Also objectives are important, so if you won your lane and took the tower down go crazy and gank the other lanes. Dragon is important as well so keep an eye out for it, I wouldn't let the enemy get too carried away with it.
Also if the enemy team is getting elder drag but they are much more stronger than your team it sometimes works to NOT fight them and instead take Baron while they are distracted.
Another tip, if your tower is about to get destroyed sometimes its worth backing off than having your tower AND yourself/team mates get taken down with it.