Optimize everything (useful video)
"And when will you make games?" — someone asked, but still got hooked on the optimization video 
Found a great video that tastefully and clearly demonstrates optimization principles in the context of gamedev. cache-miss, impostors, instancing — topics that often scare beginners, but are presented so well here that you understand them immediately.
We agreed: if a beginner can explain things even this well — that's a huge plus. And for experienced developers, it's useful to return to the basics from time to time.
Link: