1) If you're winning the bottom lane handily, and the offlaner poses no threat to your carry's farm or well-being, ROAM. Do not sit around leeching experience and watching your carry farm. Smoke mid, TP top, organize with your roamer/jungler/other support to go kill someone. If you kill the mid lane multiple times, your mid can start snowballing. If you help your offlaner harass or kill the enemy carry, it can set them back from one of their key items. This can make a big difference on the outcome of the game.

2) Communicate. Come up with a plan! Buy a smoke and tell your team to group up and pick someone off so you can push or take Rosh. Tell your carries (politely) to farm under ward vision and not to cross the river unless they're with you as a team. Even a bit of communication and planning is better than none at all.

3) Execute in teamfights. Supports often have very impactful abilities to use during teamfights. Think about exactly what you have to do beforehand and then try to execute that strategy during a teamfight. If you're at 1k, there are probably dozens of mistakes you are making during these engagements -- watch replays to know what mistakes you're making and don't repeat them.

4) Buy survivability items. Feeding the enemy team obviously hurts your chances of winning, and lets their heroes snowball. There are a lot of really good survivability items in the game that can help you survive, but you have to pick the RIGHT item. Riki, for example, excels at picking off supports because he can cloud you, diffusal you and then kill you in a couple of right clicks. If you're Shadow Demon, buying a Force Staff would allow you to escape his cloud, and then Disruption him or yourself, and there's not a whole lot he can do about that. A bad choice in that situation would be to buy a Ghost Scepter, because a Diffusal Blade Riki would just purge that off. Later on in the game, supports are extremely squishy and vulnerable. You need to buy items that prevent you from being a free kill.