This is really useful in 2v1 lanes or 3v2 lanes. Also, if you're not playing jugg - make sure to take care of what you needed to do in between kills, like healing up and taking runes to be ready for the next kill - you should never sit in a lane with no resources.
tl;dw: Kill the enemy offlaner 2 times and then kick your supports out of the lane - you get solo exp and they get to gank and win other lanes as a 2 man gank duo.
Cookie originally calibrated at 1k MMR while playing with a friend. When his friend quit Dota, he decided to git gud and in 1.5 years he was able to reach 5k MMR.
Nowadays he is 6k and spends a lot of time making guides and educational streams on Youtube and Twitch. Needless to say, a guy who was in the trench and is now at the peak is the best kind of guy to teach you how to improve at the game!