You'll want to use the highest resolution possible to give you better editing options in post production (cropping, zooming etc.) You will also want to film in at least 60 FPS to prevent screen tearing (Jello effect) in your footage.
If you enable Hypersmooth this will help remove vibration from your footage but you will notice a bit of movement on the horizon as the camera compensates, but it's well worth it compared to shakey footage.
Another thing to do is to enable Protune, this will increase the bit rate at which the camera records which will result in a higher quality video. If you're going to be doing post production you should set your ISO to 400, sharpness to medium and GoPro color profile to Flat (all found in the Protune options). However if you're not going to be doing post production, you can enable the Protune mode but don't adjust any of the settings, so you get the higher bit rate without having to spend much time doing color grading etc.
I would also make sure you use the GoPro app to frame your shot through a live preview when you mount the camera, this will help you get the best setup for your shot.
Make sure you register your camera with GoPro and check out the forums there if you have any issues. GoPro also just released a new Firmware update for their camera (1.

, so make sure you're using the latest version on your camera as it addresses a couple of issues.