Personally, I do the following:
On the street, always project a quiet but aggressive image. An oxymoron? Nah... just look like you are more than prepared to tear the next person to
mess with you a new one, and even large groups of teenagers (you know, the 'well 'ard' types) will be like the Red Sea to Moses as you approach. I
wear a perma-scowl on the street, which helps convey the 'don't mess' image. Using this front does not imply that I go around giving it the large,
but rather, I go about my business quietly and in the most direct manner, showing no fear and quiet determination. Attackers hate a confident
target.
I stay alert. I always know what's going on around me with regards to where a person is, and what way they are facing. My ears are my best
surveilance equipment, as I have super-sensitive hearing.
Using the sun as an early warning system can give vital milliseconds too, I find. When the sun is low, and you walk with your back to it, the shadow
of a person will reach the corner of your vision long before they are in arms length, for example, and as knives are the preferred tool, this is
obviously an important thing to note.
As for carrying a weapon? Well... I don't need to in my current situation. Nobody on my manor messes with me, and vice versa. This is partly due to
the front.
As for in house security, my place is a fortress in so far as I know all the defence points of the place, eg where and where not to swing that
ornamental Wakizashii. I have a few other 'ornamentals' dotted about, and I do a perimeter sweep every night.
Oh... and in my place I also have limited manual surveilance gear to give a bit more scope