Portability

[Fergusfan17]

How can I make my layout portable? It's pretty big.

[PaulGWR]

Build it into seperate modules, fix up the wiring and find a good way to transport it but I'm not the guy to go to for this kind of territory

[ThomasBachannRemakes]

Depends on how big, and what kind of transport

[TBModels]

Assemble your layout in screwed together sections, easy enough to take up and down the stairs, light enough to carry with another person, and also able to be taken apart whenever need be. Pro modelers refer to this as "modular" building. 

[jward]

as a practical matter. you'll want to keep your sections small, under 4 feet square, for reasons of weight and manoevreability through tight spaces like stairwells.

you may want to google Ntrak and take a good look at the system the n scalers have devised.

[GG1onFordsDTandI]

You could take a look at the NMRA modular standards for use, or to grab ideas from.
http://www.nmra.org/standards/modules/ms_intro.html