How to adjust the valve clearance of automobile engine and find a good method and experience?

The intake valve is 0. 15mm, and the exhaust valve is 0.30mm The novice uses a feeler gauge, and the old bird listens to the sound by hand. When the car is completely cold, the adjustment should be slightly larger, because of the principle of thermal expansion and cold contraction, but as long as this is the case, it is easy to be inaccurate. It's best to put down the hot car and start disassembling it, and then adjust it when the engine is still hot.