Sometimes the best thing you can do is to blend in. When you act the part and you become the part, then people will not notice you.
During a combination of physical and digital recon, I spent 2 hours on a coffee shop both surveying and scanning the customer for a project. The fact that I was dressed in a business attire and carry myself like a business person in a cafe that is frequented by hi-tech execs helped me with the project.
Like I mentioned in the guide, try to adapt to whatever environment you are. If you are in a cafe, buy a coffee, grab a newspaper, alternate between the computer and the newspaper. Observe what people are doing where you are and try to mimic what they do. Blending will give you a way to remain anonymous and not draw attention to you and what you are doing. Blending also mean keeping your footprint as small as possible. If you are sitting on a cafe or the reception of a company, do not bring out the laptop, wireless scanner, network switch, three external hard drives, etc. That will make you noticeable. Instead, try getting longer wires and leaving everything hidden inside the backpack. Just the laptop or the occasional portable hard drive will be on the table or your lap. If you are wardriving by foot, do not have the antenna visible, hide it inside the pack; furthermore, disable the sleep mode on your laptop, open your network stumbler and set it to log everything on disk, close the lid and stash the running laptop and stumbler on your backpack. Then walk. No one will pay attention and you'll have a neat log with all the networks available to you. Be smart. Learn from your environment.