Learn to draft.

You make games a lot less painful when you figure out how to draft a team. And you're more likely to win.

Quit picking 3 ADC's or refusing to pack a tank when your team doesn't have any front-line planned or grabbing next to no CC when you can see you clearly need it.

While first pick has the duty of not picking a niche or easily countered champion first (I.E., first-picking Nasus and wondering how the enemy team knew to use Riven to stomp you), later picks need to start building around previous picks.

We all get a turn being first pick, we all get a turn being last pick. So get out of the mindset that you should always be the one being built around and catered to and do you and your teammates a favor by picking appropriate champions.