Items like Truce can be used, it completely prevents others from spying or attacking your Turf (but crews outside of the Mansion are not protected).
If your robbing crew is under attack, you can always re-call them.
If your Turf is under attack, you can move your crews elsewhere to avoid the loss you can't take.
Another awesome way to lower the loss in the battle is to send your crews to explore the Prison.
Using random teleport or advanced teleport is another useful means to avoid trouble.
Join a clan and use clan teleport to teleport your Turf to the same area as your clan mate. By doing so you can effectively protect yourself from attacks.
Build Hospital to avoid confronting a powerful crew and reduce possible crew lost.