I also keep industrial areas small but many and quite widespread based on available resources each with their own slum using zone specialisation. This way you control traffic to a degree, its easier to manage from a distance (woodcutting, oil production, mining etc), pollution is less prolific in one area and each slum can be managed better with fewer civic resources.
The golden rule of this game is give yourself plenty of room in every area all the time and don't build everything jammed together like SimCity taught you. Think ahead to bringing in more advanced and larger transport links in future.