Consider the needs of industry, and the resources already available (shown on the transport ledger) when planning the next task of your Engineer civilian.
Whenever possible, site new ports and rail depots so that their one tile radius includes several commodities that you will find useful. Avoid constructing new depot whose radius overlaps the radius of old ones.
Although ports are more expensive than depots, it is often a good idea to build one on a coast distant from your capital. This port can provide a quick entrance to an entire new region, saving a great deal of time that would be spent building railroads across the whole country.
