At one point in time I was Bronze 5, now I'm in Gold 4. And it can be done without actually making major improvements to your individual skill. Here are 3 things that helped me win more games. Also, although it's not on the list, flaming people makes you lose way more games, but everybody knows that anyway.
_**Maximise efficiency in champ select**_
Have a main role, and if you don't get it don't then kick other people out of their main role. Say you want top as your main, but somebody above you in pick order takes top, so what do you do? You fill whatever spot is left. If the person below you really wants mid, the person below them wants jungle, the person below them wants adc etc. then if you be a douche and pick mid (even though you wanted top) you risk putting your whole team out of their main roles. The person below you might be jungle because he didn't get mid, then jungle might rob the adc of his main role, and now instead of just you being out of your main role, the whole team is (apart from the guy that took your top). If nobody calls a spot then pick your second best spot, but if somebody really wants a lane they are likely to play at their best in that lane.
Champ select is actually a great example of Game Theory in action. If you only think about yourself, you make it worse for everybody. And this is how major sub 20 min losses happen.
_**Learn how to be carried**_
Holy shazbut this is important. Some people are smurfs, and others just have random games where they move around the rift kicking ass and taking names. If you start to get creamed in your lane to the point where you're actually worried about going back, then rest your balls (or breasts) on your tower. Yes, you might give up lots of cs, but nobody should be going 0/7/0 (or a similar score). If you die a couple of times, then sit back and look at the game. is bot lane doing really well? Or perhaps top is winning? Start playing around that. If your Riven is 5/0 then just be weird and start following her around. You'll help more and give less gold to the enemy team in solo deaths. This might not be true at higher elo, but in Bronze and Silver it was definitely true. When you're easy to kill, the jungler will just farm you. Don't let it happen.
Support is only boring because you're probably crap at it. Playing support matters, and a good support can carry the game. In all of the divisions I've been in, support has been massively important. I went on a 12 win streak with Sona, all because barely anybody bothers with support or playing it properly.There are fun support champs out there, with Blitz and Tahm being the funnest imo, so learn to play them well. If you're bad at support then don't pick something like Ali or Leona though, you'll die. So learn to play support properly.