Resolution
Most modern cameras offer a variety of shooting-options: HD (1920x1080), 4K (3840x2160) or maybe even 8K (7680x4320). Even if you're delivering in HD, it can be useful to record in a higher resolution, and downscale the footage when editing. This way you'll end up with a more detailed image, and gives you room to reframe or stabilize footage afterwards without noticable quality loss.
Do keep in mind though that your computer and must be able to handle the higher resolution and larger file sizes. Also check if the higher resolution doesn't come with its own drawbacks, like worse autofocus or a cropped image. In all of those cases you might be better off sticking to the lower resolution recording mode.
Some cameras are capable of downscaling the full resolution of the sensor to a lower resolution file (for example 8K to 4K). This is called "oversampling" and can give you the best of both worlds: a very detailed image, without the massive file sizes or processing power required.
Frame rate
The third choice you need to make before you start shooting is choosing your frame rate, or the number of frames per second your camera records. In North- and South America, the standard frame rate for video is 30 frames per second (fps), and in the rest of the world the standard is 25 fps. Cinemas traditionally use a frame rate of 24 fps. The frame rate you choose has an effect on the way motion looks in your films, so if you want your movement to look cinematic, it's best to stick to 24 or 25 frames per second. If you're planning to shoot slow-motion footage, use a frame rate of 50 fps or higher, so that you can slow it down afterwards.