Hopefully this will be stickied at some point, but I want to make a thread of tips that will ensure that either you don't lose, or that you'll at least do decently well even if you do lose. (I've gotten over 20 kills, less than 10 deaths, and lost. And as more than just Darius >.>) Anyhow, I'm curious on the community's input as well, and I'd love to add in more.
I've just got done (last night) having a perfect match history http://imgur.com/a/aar0u#0 , and for all of those who are irritated at their teammates, you can still win if you can assess well.
1. Assess your teamates' skill early on.
Let's say you gank a lane. And your teamate focuses the tank while you the squishy, you both die. Should you gank there again? Likely at some point if you're a jungler, if not probably not, but now you know not to trust him/her. In team fights, this can be an essential point in whether to stay in or not when everyone dies, and it's down to the final few, and deciding to back off or not. Situationally. Now on the other hand, if they turret dive and you go "WTF?!", but they get the seemingly-impossible kill and survive? You know that's someone you can rely on. When the team is wandering late game in groups (you know this phase), this is the person you want to be with.
Everyone says it. It is EVERYONE'S job. Not the support's. Not the jungler's. Everyone's. They just have a higher responsibility for it. My general rule of thumb is if in a solo lane, if you are zoning, buy 3-4 wards, and have an escape method ready-- top lane especially, mid depends a ton due to the need to outshine your opponent that much more. Bottom lane depends on the enemy jungler but either be prepared for a gank, or ward and be prepared, if you are winning. As a jungler, just ward where it's vital.
3. Know when it's your turn to enter the fight.
Not everyone should enter a teamfight initially. A tank should. A bruiser should right after. Otherwise, unless you outshine them that much, wait until their cc is blown.
4. KS=Kill Secure
If someone has a guaranteed kill, don't be an ass and take it. But if it -looks- guaranteed, don't assume it is. Flash, last-second CD's, an enemy hiding around, all of that can screw with what you thought was assured. Land the kill. But what about the gold that you just took? Assists still help. Don't kill steal, but realize a lot of the time KS means Kill Secure. Though make sure to clarify after if someone is likely to rage-- make it clear so that they understand. If they get upset, their state of mind changes, and you're more likely to lose.
So your entire team speaks Spanish? I remember recently being in a match-- the other 4 spoke Spanish. A couple spoke -some- English as well. I also saw the stereotypical "jajaja" come up-- though I think they said that jokingly to each other. I don't know; I'm not a Spanish major. I did however use pings to communicate-- they're universal. Pings can easily say "GTFO" or "attack THIS one!" Unless they're trolling that hard, you'll still do well. Talk to your team often, say what your plans are. Even if they don't care. This is especially true for junglers. "I need to go back in 100g."-- bottom lane can help; as a support, your ADC may let you take just a few creeps (don't go overboard here). "I'll be top soon, hold it, don't attack"-- mid lane if you're winning. Maybe he'll/she'll conserve health and mana so your gank will do better. "Buy a ward so I can teleport and gank"-- any lane. This is just nice to do.
Edit: As suggested by Thejoshwolf, if you are still having trouble communicating with someone who speaks a foreign language, alt-tab early on, and Google Translate "go ___ lane". It might work!
6. Trolls Will Not Lose The Game; Your Cool Will
In ranked this is different. In ranked... Well that sucks, and if you know before hand, try to get someone else to dodge, or do it yourself. Too late? Ouch. But in normals, I remember once having someone feed the entire game. And tell the enemy where we were, giving our positions away. We won. We moved when he told them where we were, and his feeding made him worth next to nothing in gold after a while. A setback, but our teamwork still won us the game.
7. Adapt Your Build
Don't build a Will of the Ancients if someone already did, unless you want it to stack between yourselves. Don't build a Guardian Angel if you aren't being focused. If you're a tank, build more damagy, if you aren't being focused. You'll be less tanky, but more of a target. Even for a few attacks, that's good. Don't build MR if their only AP is 2/10. You should likely build more Health or Armor depending on your champion.
Like I said; I'm open to more here and will edit this continually, so keep the good tips coming!