Few tips, hope it helps, I've played around ~1250 games and these are things that I wished I'd figured out earlier
1) Watch the minimap! Especially if you're pushed up far in your lane. If you're pushed up far you should more or less keep your eyes glued on the minimap (even more so if you're alone) If you see another lane is missing go back immediately.
2) Buy wards. If your supports refuse to buy them and you're a carry buy them anyways. Vision is a game winner. (once you get into higher MMR supports will almost always get them without being asked)
3) Always carry tp. From the 10 minute mark on you should have a tp in your inventory always. This has saved me countless times and also allows you to quickly get to a friendly lane that's getting ganked, often turning it around and bagging your team 2 or 3 kills. Always carry tp.
4) Harass if you're the support in lane. For example, say you've got a lane with windrunner and skeleton king versus jugg and veno. As windrunner you should be trying to hit jugg as much as posisble to force him to go back to heal or back off a bit. Try to stand a bit further away from enemy creeps (to the side) so you can get away from them before they hit you a lot. Also, you can take enemy creep aggro off yourself (and tower aggro too) by targeting a friendly creep.
Oh ya and don't be a jerk, the DOTA2 community is pretty terrible, don't contribute to it ;). If someone is making a mistake give them a suggestion nicely don't spew insults.
Post edited December 31, 2012 by NoxNoctum