With your first roads laid it's now time to start laying down some residential, commercial and industrial zones (R, C or I). Select the zoning icon then one of the options (R, C or I) and lay down according to the plan in your head, remembering not to stick industry where it's pollution will blow onto residential zones and also, just not close to residential zones either. Use CTRL as you zone to zone the whole block at the same time.
Take a look at the image below to see an example of zoning. You'll see the commerical zone provides a buffer between the industry and residential zones.. You'll also see that initially I have zoned quite large this is because I managed to take out a lot in loans and also I will plan to split those large zones with avenues at a later date.