How to Use the Underground Network?

Tunnels are not the only structures that are meant to be underground. If you're bilding a lot of underground tunnels, what's the best way to make sure that they coordinate with future projects? Is it a long range plan? Are there other ways to do it? What is our plan about the serviceability for this city? Do we have enough space above ground to provide them with retal, entertainment, anything that you do not spend a long time? In their opinion, can go underground upon a very precise planning.