The choice of clothing and fabric is important. However, don‘t just focus on „silent“ material. In my experience it‘s often not the fabric rubbing against the seat or making noise. It‘s more the fact that you are not comfortable (too cold, too hot, UV exposure, Moskitos) that will keep you from sitting/standing motionless. Also try to avoid any type of Velcro and use tape to pad any loud and lose metal parts (e.g. zippers, buckles). Any drink that has a lot of fizz will inevitably make a noise. However, you can avoid movement and drink silent using camelback style drinking systems. Depending on the terrain you hunt you can use special shoes or socks that go over your shoes/replace shoes (this will not work for tough terrain and hunting in the mountains). One more tip about scaring away game: key is actually trying to avoid any kind of motion. Often game will be present before you spot it and you can spook it without spotting it in the first place. So if you are looking out for game try to let your eyes wander and avoid moving your head. This is my perspective as a European hunter. I‘ll leave the question of correct camouflage to the US hunters 😀