First things first, I'm getting my family together and a few close friends. This would admittedly get a group of 20 or so people together which is kinda hard to feed, but it's better than being dead. These people each have building and thinking skills, they're loyal to one another and, there is safety in numbers.
Then a base of operations is needed. Preferably something with a screen so it's hard to see. Perhaps a forest would work or a single building in an industrial zone. Make no observable defenses as the first defense is stealth. Build choke points so there's one way in. Find a hidden way out that is almost impossible to get up to, (a jump into a river?). One way in, two ways out.
As for fighting, all these fellows talking about big swords or guns... nah. We're going to get some pointy sticks and learn how to use the sling. The stick gives superior reach and can be used in a variety of utilitarian ways, digging through rubble, finding a safe path, and most importantly keeping things at a distance. Make one end pointy and you've got a good deterrent for any charging foe. Have a friend backing you up, and now the foe has one weapon to deal with two pointy sticks, not good. The sling offers a silent hunting tool that is easily transported (worn as a belt or wrapped around forearm) with plenty of ammunition (stones) about. Lead or other steel marbles could be used if needed for more challenging targets.
Food is the biggest issue. I have no interest in hurting people, so I would rather try to farm. The farms, to continue with stealth, need to grow somewhat wild. So haphazard planting is needed. Animals need to be hunted with care so that the area resembles a dangerous wildland. The more dangers, the better as we will learn how to live with them and the dangers will scare away the wanders who may cause harm. Fishing is likely going to be very important as it's a food source that can't run away and thus look suspicious.
Past that, I don't know.