[Ankesh]

Thanks for asking Griff.

Only you - or someone living in your town - can answer that question for you. Because there is no generic answer. The answer is based on your town people's behaviour.

Gordon's rule of thumb is: people will usually travel not more than 30 minutes to get what they want. Going with that rule of thumb, you would bunch all the zip codes that can be travelled across within 30 minutes together.

But I stay in Bombay. 30 minutes travelling during peak traffic is a lot different than 30 minutes travelling during off-peak hours. So we can't rely on time a lot. We have to rely on distance. In Bombay, people won't travel even 2km to do their grocery. So most local consumer businesses focus on just marketing in one street / neighbourhood. They don't even try to canvas one entire zip code - just part of it.

Start with people's behaviour in mind. How far will they travel in your town to get a better deal? That is your target area. It may mean 2 zip codes or 40 zip codes. Only someone staying in your town can answer.