I think that a living town is first and foremost a town that has some interesting NPCs, and in addition there are some things that are happening there, affecting the NPCs and being affected by them. As such is the case, I usually divide my town-fleshing into two parts: Fleshing NPCs and fleshing the surroundings and town.
I'm an improviser kind of GM. As you are, according to your own words, a lazy GM I think that I might prove helpful.
Fleshing the NPCs
I don't plan my NPCs beforehand. I create them as the need arises and discard them when the need disappears. In order to flesh characters there are a few improve tricks that I've learned.
- Use strong emotions. People are emotional beings and this means that they feel quite a lot. Whenever you portray an NPC, go for a strong emotion and he will feel like he feels something. Most of us play those feelings in a level that is too low. Try to change that, make the emotion almost scream from your face and/or gestures.
- Use a guiding gesture. Try for once to talk without moving your head, make it still. Suddenly, you've created a character that is high status. Try to sit differently, or use a recurring gesture, and you'll feel that the character takes a life of its own.
- Voices. While I'm not that great at voices, this is a sure way to differentiate between characters, and/or to make them come alive.
- Words use. We people use different words in different ways and in a different amount of times. I, for once, don't curse. My sister used to curse for me, as I once joked. Use different words and you've created different NPCs.
All of this is important because the inhabitants of a town or of a city are the thing that is most responsible for making the town come to life. After you've mastered that, or even before that if you want, you can do some other things in order to…
… Flesh the surroundings and town
This is an umbrella term that I use to describe everything in town that is not a single NPC. Some things that might help you:
- have a certain similarity in names. Whether we know consciously it or not, there are unique sounds to names from a very close area. Use it to your advantage. Maybe in a certain town all the names starts with the letter J, in another one female names are for males (and vice versa) and in a third one all the names are French. Suddenly, you've got a uniting theme that makes this town distinct enough form the others.
- Have a special Holyday the first time the characters come to visit. I once had a town that the PCs visited in which the townsfolk celebrated Apple-Pies' Day. To this day they remember this town. Even when they visit afterwards, it is still the town of the apple-Pies' lovers. Or think about that town in Avatar where they celebrate the "Day of the Avatar". Surprising the characters with a holyday that is far less naïve that it seems can prove even better for fleshing the town.
- Another idea is to have a certain building or architecture style that makes this town unique. I once had a town in which the roads and streets were a literal labyrinth. In another I had a huge library of seven levels, all filled with jewels, gold and books. Have something special in the town or in its surroundings, and you've got something.
- Have the town under attack. Players like to feel heroes, and their characters are heroes. Use that, make them save the town or the city and suddenly they feel enough for the town to make it come to life by themselves. They will breathe life into it.