Prick sausages 2-3 times on each side with a fork. This stops them bursting as they get hot and allows fat to escape easily.
I use a roasting dish or a flat casserole dish for this, depending on how many I'm doing. Place the sausages in the dish and pour in water to a depth of 1 to 1.5 cm. Place in the middle of a 180C oven.
Inspect from time to time and as soon as the sausages show signs of browning on top, turn them over. You can repeat this process 2-3 times. Towards the end of cooking time most of the water will have evaporated and the sausages will be cooking in their own exuded fat, much of which will remain behind in the dish while you get stuck into the rest of the sausage .
You can do this, too, using a covered heavy-base frypan on top of the stove, where the (loose) lid allows steam to cook the upper part of the sausages, and also allows it to escape as necessary. You may need to add a little extra water from time to time, and you will need to turn the sausages over to get even browning. Using this method they brown on the bottom first.
What I like about this process is that you preserve the particularly delicious flavour of sausages browned in fat while actually reducing the amount of fat in the finished meal. You can do this of course by boiling them first and then frying or barbecuing but this is a one-stop-shop as it were.