After so many tries and googling how to upload program to ESP-12

I would like to share my wasted time, I was lucky that my board still working after many wrong tries

Step 1: Programming Mode

To upload a sketch via Arduino IDE, Connect as the picture above!
Don't forget resistors you can use from 6.4K to 20K (10K recommended)

Step 2: Normal Use Mode (after Upload)

You can back to normal boot by disconnect pin GPIO0 from GND

also, you can disconnect GPIO2 (optional) but DON'T remove GPIO15 (always pulled down), also don't remove EN pin ( always pulled up)

Good luck