Often there's a lot of talk on here about good team mechanics, which heroes work good together, and general things that work well when you're playing with your friends. But the fact of the matter is that you aren't going to be playing with arranged teams all the time. Generally you'll be playing with random people who most likely hate you because other random people they've played with have established a track record of being absolute cocks. As a solo queuer, you're generally starting with essentially negative teamwork (especially at lower MMRs). People on your team will gladly sacrifice you if it means they can do better.

So how can you do better in these situations? You become the team captain. Note that the team captain isn't the highest rated MMR person in the game - it's simply the person who has the confidence to call the plays and ensure the team is communicating. You can be brown/orange and still be team captain. Here's some quick points:

1.) Focus on building a team in game
This is most often the biggest thing that's overlooked. Everyone in a pub game is coming in with their own goals and plans for end game. If you want to win, you have to make sure that everything you're doing is in sync. Ask everyone what their build is going to be. Make sure you dont have two people getting a radiance or two demonic breastplates on the table.

2.) Stop fights
Your team will bicker. Having two people call each other noobs just makes them both play worse. Politely put out the flame war. Remind them to focus on the fights at hand.
"Hug it out guys, we dont have time to bicker. We can turn this around easily if we focus."

3.) Start fights
Stuck mid with both parties dancing? Get on that mic. Give orders and tell people what to do and when. Let people know what to expect in a team fight before it happens.
"Earthshaker, drop into that mid crowd at 19:45s, I'll bubble you right before you blink, and drop my ult once everyone is in. Rush in as soon as you see him blink people."

4.) Get a mic, keep your mic
If you dont have a mic, get one. They will change how you play the game. Also though, be respectful of the other people in the game. Dont scream or be annoying. The worst thing you can do is get muted by someone. As soon as they tap that mute, you've lost a team mate and gained an enemy of your enemy.

5.) Keep checking in on people
I rarely see this in games, but every once in a while it's good to check and see how people are doing in lanes. Just because someone is 1-0 in a lane doesn't mean they're getting the farm they may need.
"Hey top, how's everything going up there? You getting the GPM you need? How's the other team's farm out there?"

Above all be respectful to people, even the other team. Drop your G's if you must, but dont be a dick about it. The metagame is just as important as the game itself.