Insurance & law
Never go back county alone or without adequate Insurance, check the small print make sure it states back country or off piste. If you brake a leg and need airlifting out you're going to be paying for it for a long time if your insurance won't cover it.
If you are going on a pre-organised trip with a specialist snowboard or ski organisation, check their insurance cover. Find out if their instructors and guides are properly qualified with a recognised certificate and have public liability insurance.
In Europe, you are warned not to ride outside restricted areas. However, you are seldom stopped and in many cases it is not actually illegal, although some areas are National Parks and therefore protected, get caught in these and you could get a fine. In France if you set off an avalanche which ends up killing someone on the piste below you'll be charged with manslaughter.
In the US and Canada, riding in marked-off areas is simply not tolerated. The patrols are extremely strict about riding "out-of-bounds" and apart from getting yourself kicked off the slopes, you could also face police charges.
Back Country Terrain can sometimes be accessed straight off a lift or you may have to hike to it. Both should be treated with the same respect just because you hopped off a piste doesn't make it safe. Choosing the size of and who's in your party is very important. When hiking four is a good size for a group it's easy to monitor each other and if someone has an accident one can stay with the casualty and the other two can go for help. All members of the party must be competent riders, be trusted to keep cool and help if it all goes belly up and most importantly have the correct equipment and know how to use it. It's also important to have an experienced party leader, decisions on route finding and if you should turn back or change the objective should fall to one person. Never split the party unless you need to send for help.
Next: Avalanche & Rescue