Be judicious with details.
Remember that your print will be small, and that the printer itself has a limited degree of precision.
For example: showing a cornice is wise, but ensuring it has every curve of the Corinthian order is probably a waste of time.
Keep your model clean.
Holes, stray lines, and extra planes within the model will be difficult to edit out later, and must be removed to ensure a printable model.
Think of your model as a shell.
The printers will treat your model as a solid volume, with a smooth outer exterior and triangulated infill interior.
Don't add floor plates, interior walls, or anything you wouldn't see from the outside--but DO close the base of your model!
Be careful with overhangs.
The printers work from bottom to top in flat layers; any overhangs, loggias, etc. will have difficulty printing on air if not supported below.
Consider splitting your model up into groups from the beginning, as this is more time-consuming the further you progress.