You must used a stabilizing gimbal.
Or if don’t have one for that copter/camera (like some of the bigger cameras), pick a copter tilt (attitude) and stick with it throughout the shot - don’t change the right-hand stick in any direction through the shot.
Frame the shot so the Drone’s shadow is not in it.
These can be taken out in post, but it is a serious pain.
When doing scenery shots, make any pans and tilts very slow and steady.
When in doubt, pan or tilt even slower!
Avoid getting a prop between the sun and the lens.
Otherwise you’ll get a flicker in your image. This can be avoided with a sunshade or lens shade on your camera. Or you can just frame the shot to avoid it.
When getting a terrain shot, try to make sure the horizon or any mountains are in the shot.
Often a shot has the horizon or mountains cut off, which is not wanted most of the time. However there are many reasons to leave as-is, such as the subject of the shot is below your copter, etc, etc, so use your judgement.
Shots that are obviously drone shots are better than just “regular” shots.
In other words could the shot have just been someone walking or standing with their camera hand-held, or a regular ground-dolly shot, or a guy on a ladder, or a guy in a boat? If it is a super awesome shot of something, ignore this point!
Add a little bit of motion to scenic shots.
It is usually good to have some lateral or vertical copter movement, so it doesn’t seem like the shot was simply taken from a ladder, or a building, or a roof, or a boat. This is not always the case, depending on the shot, so use your judgement.
Shoot at 30 frames per second or higher (or 29.97 if that's what you have).
Stock footage is used in many ways, and so it is good to have as high a frame rate as possible, which can be down-sampled to lower rates if wanted. For specific projects however, check with the director on FPS that they want. The typical film (motion picture) framerate is 24. Typical TV, commercial or web videos is 30 FPS. Thus if you don’t know, best to shoot at 30 FPS, so it can be used for more things.
Try to do one camera motion in each shot.
Do one motion if possible, no back-and-forths or multiple moves and changes of direction. A slow pan to the left at the same speed. A smooth tilt up and stop. Or just do no tilt or pan throughout the shot; don’t underestimate how good a shot can be by picking a camera direction and leaving it there throughout the copter move.