Video: Some solid tips on movement and peeking angles. voo CSGO shows some of the mistakes new and even experienced players make a lot (strafing by using W too much for example) and how to fix them.
Checking angles and positions is indeed the key to become good, and no matter how popular CS:GO is, tricks like these aren't common knowledge among new players.
It's worth checking out voo's other videos for some more advice. They prove there's so much depth to the game's mechanics.