D@rth, at the risk of sounding a bit smart-bothered, it is relatively easy. The hardest and most important aspect is patience - taking time to do each little thing properly. In that respect, it's no different to any other aspect of our hobby. The more attention to detail, the better the end result.
But the basic methods are simple...
If anyone has any questions at all about anything I did on my town, please ask - either here or on my blog. I'll be only too happy to elaborate!
Colonel O'Truth