NEVER GO INTO A RANKED GAME WITH THE MINDSET THAT YOU ARE GOING TO LOSE. I have friends that I stopped duoing with because they would enter with that attitude and often it would end with us losing. You have no idea how much difference a positive or even a neutral attitude can make. Instead, go into the match with a solely analytical attitude. Ask yourself, "At what point will my opponent be stronger than me? When do I need to play safe, or ask for help? What does our team have for strengths? What strengths does the enemy team have? Is there a point where we need to win or be ahead by?"
No matter what shape your team is in, NEVER SURRENDER. In elos like bronze-gold, people have no sense of how to extend their leads, and they can often be caught. If you're behind, extend the game as long as possible. If you can make it to the SUPER late game where everyone is full build, gold no longer has effect. It often comes down to a single teamfight once the death timers max out. That being said:
KNOW WHEN TO TAKE OBJECTIVES. If you can, gain a positional advantage on your opponent by taking a tower. DO IT. Towers are nearly always a better use of your time than taking dragon. Towers give global gold to the team which can sometimes be the difference between coming back to lane with a full item or not. The dragon buffs are nice, but as long as the enemy team has 3 dragons or less, towers will provide you with a stronger advantage.
LEARN TO BE THE SHOT CALLER. Your team won't always listen to you, but having someone making calls on whether or not to fight or when to take an objective can be the difference between winning and losing.
YOUR ENEMY MAY HAVE A STRONGER CHAMP. If you can avoid giving them kills early and farm under tower, you can often kill them with help and begin to give yourself an advantage. Most champions with an strong early game will fall off eventually. If you can build yourself a lead where you can safely farm in lane, you have a good chance that you can out-scale them and take control of the game where you can carry the game yourself.
FIND CHAMPS THAT SUIT YOUR PLAYSTYLE. I have a select few champs that I play in ranked. I feel comfortable playing them into their strongest counters because I know my champion that well. That is the comfort level you eventually have to reach with the champions you play if you truly want to improve. I have 2 champions in each lane that I feel comfortable playing in any situation. Don't just play champions because they counter an enemy. I would also suggest trying to find at least one champ that you can carry on in each lane just in case it is necessary.
You have probably heard most of this a million times, but this is really what it comes down to. Now you can say, "but you're only silver, why should I listen to you?!" You don't have to, but know that rank isn't everything. I choose not to play ranked because it brings out a much more competitive side in me that stops me from just enjoying this game that I love. Also I know what needs to be done, but even I sometimes struggle in executing. Higher elos will probably tell you most of the same things.
Best of luck on the Rift my friend,
King Wanahakalugi
and he helps me get out of bronze