I have a hard time with being unnoticed, need to work on that. Some good posts made, I appreciate that.
Good spies didn't look like Sean Connery or Pierce Brosnan... They looked like the guy who handled your mortgage paperwork at the bank... Unremarkable.
I'm 6' 220ish, brown hair, blue eyes, no tattoos... I have facial hair but nothing that stands out. I (usually) keep it trimmed so that it's pretty well hidden behind a mask. I don't wear jewelery at all. I wear glasses but they're such a common style that hopefully they're unremarkable.
The trick is to wear clothing that is "in style" but don't pick the most expensive or outrageous/brightly colored articles. A pair of comfortable jeans and a t-shirt. Throw on a black or grey Nike/Adidas/Carhartt hoodie and similar ball cap. Footwear should be sensible and comfortable but keep it nondescript... My daily work boots are a pair of moc toe Thorogood work boots. They're good boots but not a lot of folks outside the trades wear them and they're ugly enough to be remembered. I also have a pair of soft toe Wolverine wellingtons. A bit more low key and forgettable.
Be polite to people but not talkative. Being too quiet or ignoring a 'hello' may mark you in someone's memory. A polite nod and a 'how ya doin?' when someone says hello may help you be forgotten. Don't have stupid/annoying/memorable ring tones on your phone. Stopping to check a message or notification is almost ubiquitous in today's society and it gives you a chance to stop and check your surroundings without drawing a lot of attention.
No one should know you have a knife and CCW until it's too late.
The customized Covid masks are all the rage. Wearing one helps you blend in but choose something plain... Avoid the American flag, Punisher skull, flippant edgy messages, and all that crap.
Body language should tell people you are moving somewhere with a purpose but don't look like you're trying to be sneaky. Hands in your pockets, hunched shoulders, and head down looks like you might be trying to hide something.
Be a "people watcher" when you can. Learn what makes people stand out in your memory and what doesn't. Apply what you learn.
Mike