So for outdoor stuff with an external flash it helps to think of the shot as two exposures:
1. environment exposure, which is exposed by ambient light and the settings on the camera
2. subject exposure, which is exposed by the power settings on your flash.
Outdoors during the golden hour is tricky in terms of lighting because the sun is setting so fast so I automate things as much as possible and shoot in AV mode and ettl. So in AV mode with ettl, the exposure compensation dial manipulates the exposure of the environment, and the FEC manipulates the exposure of your subject. With that in mind, since everything is pretty much automated, the main thing you need to consider is the spread between the cameras exposure compensation, and the flash exposure compensation. The greater the spread, the more contrast between your subject and the background. The ambient light also acts as a fill light, so the bigger the spread, the harder the fall off of the shadows on your subject.
I typically like a 2 stop spread, so my camera exposure compensation dial is set at - 2, and my flash exposure compensation at 0. Of course I'll adjust in the field based on how things look when gimping.
advanced level stuff
In terms of exposing the ambient, the same concepts used when shooting landscapes apply, so if you want to retain the highlights in the background (usually color in the sky), you'll want to use ETTR method. I usually look at the scene like a landscape first, then add my subject and consider the subject exposure second.
Even if you adjust the camera exposure compensation to retain ambient highlights, keep the spread in mind. So if you want to keep a 2 stop spread between your subject and environment, if you end up needing a -3ev on the camera to retain the highlights, you'd set the flash to -1. When you push the exposure in post, you'll still see the contrast between the subject and background, but can pull back the highlights to get detail in things like the sky.