When I first begin I usually stay on the edges of the cities, or stick to the "suburban" areas with lots of houses and not so many stores. The loot is worse and more randomised, but you'll find lots of food and enough tools and weapons to gather a decent early game collection. I don't have any data on the matter but I feel that there is a lot less zombies spawned in these areas too -- with the exception of failed survivor houses, of course. Stay away from those.
Most importantly these areas allows you to move mostly unseen through houses. Windows only let in enough light to light up the nearmost tiles so stick to the other end of the rooms and you'll be a lot less likely to be seen from outside. House windows nesrly always have curtains -- if you carefully approach them from the side you can close these (I believe with the examine key) and zombies won't be able to see inside at all. Move from house to house at their sides to minimise the chances of being spotted outside.
But what about sound, you ask? Crashing in windows and beating down doors produce a lot of noice. For doors, one of the first things you want to do is craft a bunch of makeshift lockpicks. These can be made from scrap metal. For windows you want to make a makeshift crowbar, all you need is a pipe and a stone. Crowbarring windows open still makes some noice but a lot less than smashing them would, and you can still close them and close the curtains behind you once you are inside.
And lastly a cheesy trick: MI-Gos are pretty tough, but you can outrun them (you can switch between running and walking with a key... can't remember which it is off-hand. Maybe 2?). If you find one near a town, you can lure it to a city and use it as a troll for all the zombies. You're faster than both and can keep ahead of them, but the mi-go is faster than the zombies so it will catch up to them if they're between it and you and kill them for you. You can clear many tiles this way before the zombies manage to take the mi-go down.