I hear a lot of pro LoL streamers say that to be successful in ranked solo queue you have to "Act like your team has no idea what they are doing." What exactly do they mean with this? How can imagining this benefit you?
Because you are in solo queue you an not expect wards, ganks, or your teammates knowing when to do objectives. If you notice any of these things being an issue all you have to do is politely inform your team.
Nothing keeps people in ELO Hell longer than being rude and cussing people out because they did something wrong that you never informed them on.
The reason this is what they says is because you cannot depend on random people. You have to make yourself believe they know nothing and you have to guide them to victory. This benefits you because if you depend on your team and they don't know what they are doing (which happens a lot) then you are screwed. So you must take matters into your own hands most games and assume as they say "like your team has no idea what they are doing."
It means that you shouldn't expect that your teammate will notice you coming for a gank unless you ping. It means that although you see 3 people walking through a ward toward a teammate, that teammate does not see it and needs you to ping him to back up. You shouldn't expect that your jungler knows that you can easily kill your lane opponent with a gank. You shouldn't expect that your team knows anything other than what you tell them. Act like they don't, and you will get killed less.
What a lot of these high elo streamers have said in interviews is that you need to know how to lead your team. This does mean you have to assume that they don't know what they should be doing and how to capture objectives, who to focus in teamfights. Don't be rude about it however, but just ping dragon, and say let's dragon or help at dragon in chat. Anyone playing ranked games should know dragon and how it gives gold and who doesn't like gold. Just need to make yourself the leader of the team, because when both sides play with random players, the team that communicates the best tends to win the game. Communication isn't easy, and the easiest role to take is leader if you want to affect communication the most in terms of a coordinated team.