Warding, and bitches.

http://www.team-dignitas.net/articles/blogs/DotA/1092/Dota-2-Ultimate-Guide-to-Warding/

Everyone should read this. In general we're not that good at warding. First we need to get knowledge about warding, then we need to consistently buy wards whenever the cooldown's down then we apply all that in a game. You could try setting up some wards in the practice mode if you'd like.