Just thinking (yes, it happens) about the most useful bit of information I got from BC. I can't find the thread but it was about serving in doubles and NOT using the sweet spot. My serve was already good but that piece of information helped me get it to another level of consistency. What is yours (doesn't have to be technique)?
Yes, here... http://www.badmintoncentral.com/for...t-point-on-racquet-head-during-backhand-serve Plus there's a video of Cai Yun teaching how to serve in which he mentions the same. The strings being tighter near the racket edge is great for both feel and consistency. Plus it's closer to your shuttle hand so the shuttle can be practically hit (preferably pushed) out of your hand without the shuttle dropping much, which adds to the consistency.
Most useful info for me... must be the Badminton Bible. That helped many of us understand the basic grips, strokes, etc. of badminton... Not to mention thejym's pronation video on YouTube. That helped me understand that concept better. Which I've also applied to the supination in backhand.
I guess I have to nominate the "Badminton Stringing Techniques and Tools" Sub-Forum in total. Without it, 1. I would have never even developed interest in stringing at all 2. I would not have bought a stringing machine 3. I would not have been able to even finish one single string job 4. I would not have achieved some decent consistency in such a short timeframe So a big thanks to all who are contributing with so much expertise and so many useful tips there.
Hard question to answer. Limiting it to recently most useful, I'd say the same as s_mair. I started stringing recently, and the information here is really useful. Kwun's stringing videos/tutorials in particular helped a lot. Thanks! I feel honoured.