/mute all helps and all but sometimes your team has something they need to say to you but if you mute them it just ruins that. Rather than muting people right off the bat, just ignore anything stupid they say and don't let it get to you.
Turn all chat off though, the other team will only try to tilt you.
You should try to fully understand your champ's play styles and roles in the game too, such as Shaco. Shaco is great for split pushing or assassinating high value targets. If you cant win team fights then just focus on split pushing, save ult to dodge or trick the other guys and use Q the same way. Set up boxes in the lane and jg area around the lane you are split pushing in.
Don't try to get good with a HUGE champ pool yet, focus on your main 3 champs for your 2 main roles for about 6 champs that you can play. When you feel comfortable with those 6 then expand it and keep going until you have a large champ pool that you are both experienced and skilled with. (this tip isn't that important but I found it useful.)
YOU ARE GOING TO LOSE! You can't win every game so don't let a stupid loss make you quit and just move on to the next game. Never surrender because the enemy team can throw at ANY time. Play safe and don't do anything too risky unless you are confident.
Pretty much all I can think about. GL and add me if you ever want to play some matches together.