Blending in.

The human brain becomes aware of things that stand out due to the reticular activating system sending your brain a message that something does not belong. Certain things can work to reduce or increase this response. It is very situational. The same biker that stands out in a mall would blend in at the right bar. Some stimulus have a grey effect and tend to be overlooked. If you look for these patterns you can train your mind to become alerted to things that seem to blend in too well. Facial expressions, posture, clothing, and situation all can be applied to a metric and if a subject it too average they may be greying themselves out and therefor trigger your trained response.Any information on blending, counter blending and the subject is welcome.

Use earth tone colors. Colors which work good are grays, tans, browns, and navy blue. Avoid bright colors and avoid black; nothing in nature is solid black. 

Walk at the same speed everyone else is walking at. If everyone starts running and screaming all of a sudden, you should too. 

Put ear buds in your ears and pretend like you're listening to music. Wear sunglasses. Chew on some gum, flip through a magazine, and stick to the shadows. By appearing to block out your own sensory perception, other people's brains will be less likely to register you as potential threat or as something novel or out of place. The reason for this is because the brain registers you as inferior, and immediately throws your image back into the dark recesses of its attic in favor of something more interesting than boring old you. This is also a good way to get people to leave you the heck alone; people don't engage other people who appear to be busy with something unless the situation demands it. 

This principle can translate into all manner of disguises; people that everybody else by and large just don't care about or pay a second glance, or even a first glance sometimes. Construction/maintenance workers, janitors, store employees, clerks, security guards, cops, firemen, doctors, ANY uniformed official. 

Other professions and or places of business have a typical dress code/fashion that almost constitutes a uniform. Lawyers and businessmen alike wear nice suits and ties, whereas lumberjacks wear plaid shirts, jeans, tool belt and hiking/work boots and gloves. All depends on where you are/where you need to be. 

Also, wherever you are, walk with purpose as if you actually belong there and are supposed to be there.

Homeless people are also a good disguise. You can disguise yourself as a homeless person by trading clothes with a homeless person.

Diversionary tactics and distractions are also tools that would seem to aid this practice. The image of the thuggee team, one pointing at a distraction, one holding the hands, and one preparing the garrote comes to mind.

Pulling a fire alarm. Putting a smoke grenade under a car hood. Fake medical emergency of some kind. Switching off all the Breaker switches. These can all cause a commotion that enables one to slip away in the ensuing chaos while everyone is focused on something else. This shouldn't be done lightly. It's really mean and inconvenient for a lot of people.