Wow, some amazing suggestions here. I understand the frustration of the leavers/feeders in solo queue, and I have learned how to combat this pretty well. I play jungle. In the event of someone arguing over who tops or mid or whatev, I will call Jungle. Most of the team issues arise before the battle even begins. I ward as much as I can to help the person being ganked constantly, and can fill any leaver position rather quickly. My track record isn't perfect, but it does help. provide wards for those who are dying a lot, offer suggestions of support rather than critisizm and NEVER complain to the other team of someone being AFK. They can use that to their advantage rather than being more conservative when they fear a gank is around the corner.
Do your absolute best to make sure you stay positive in a game, and find ways to help others stay positive as well. Give a buff to one of your players, ward for them, help in a gank and you will have a great team vibe and a MUCH better chance at winning/surviving a game.