When we arrive the routine goes like this:
Airplane mode for all phones/tablets unless in use Turn off Dropbox syncing (all devices) Turn off Backblaze (cost us about $100 in data last time we forgot to completely disable) iOS updates for our 4 smartphones? Wait until we return home Disable app updates (some are several hundred MB) No Pandora/Sirius streaming or audio streaming of any kind Limited Netflix/Video streaming (only for must watch shows) No large FTP transfers (common for our industry) No Facetime (our kids use) Schedule Dropcam power to turn off at night Block podcast downloads within iTunes The list goes on....
So basically every day you check, and recheck your data use to "catch" any device or service that may be using too much data. When family visits and the number inside the house reaches 6-10 the monthly data cap is blown in just a few days.
And our data cap is not a measly 5GB or even 10GB a month, it can easily reach 40-50GB which costs a relative fortune.
If you look at the list of accommodations above, you'll see a nice collection of US businesses (Apple, Dropbox, Pandora etc.) for whom I can't do business with in a "metered" world.
I can deal with this for 2 months out of my year, but if my home residential Internet was also metered like this our involvement online would be dramatically changed.