1. If you're shooting late in the day with that beautiful gold contrast light, as the sun goes down.
I am often in this situation, but still need to shoot pictures that day. On a shoot in Western Australia for a swimwear catalogue, we were shooting our last collection but the sun was going down very fast. I still had four shots left to take. So, I had an assistant hold a 1mtr gold foil reflector up to the side of me, so if I aim a flash gun onto the reflector it would bounce lovely golden light onto my model. I set the flash exposure to be about one to two stops under the ambient reading taken from my models position.
This is one of the shots taken this way.
2. If you're shooting inside on a really nice, bright day and have a lovely window that would be great to shoot your model next to.
Take a long 1x500 watt flash head with an 8-inch reflector attached. When you've set up the model's position, take the high light reading. Let's say it's f11 at 125th sec. Aim the flash head at a nearby wall, if the is one (as long as it's a neutral color i.e. white or grey). Set the power of the flash very low so you're getting a flash reading on your model of f5.6 to f8. This will give you a very natural-looking fill in flash. If there are no walls or there are strong colors, take along a large reflector and put this in place of the wall. Aim the flash head at this so the reflected flash light bounces onto your model. Try it on a test shoot before you do a serious shoot, so you're confident of the results. Each place you shoot will give you different results, due to many factors such as the walls, ambient light and the color of room. So, don't expect to get the same results every time.
Here is a shot that was done using this technique.