Chose a quiet location, less background noise to ensure there are no distractions. A white or plain coloured wall will keep it professional and uncluttered.
Stand facing a window if possible to highlight the subjects face. A lamp or light shinning light down on the subjects face positioned behind the camera will work if there is no access to natural light.
Video cannot be a selfie. If using your phone it cant be handheld. It needs to be positioned either on a device (tripod) or against and object (e.g. stack of books) to ensure there are no micro shakes on the screen.
Camera should be held horizontal (Landscape).You can load both but IGTV is more for suited to vertical. Shooting it in landscape means its easier to put it on other platforms like YouTube.
To ensure that the subject is in focus and evenly lit. Have the subject hold down the screen on there face until the focus and exposure lock (on the IPHONE this will appear as a yellow AE/AF lock on the screen. Avoid any shadows cast on the face.
Ensure when recording that the camera is level or just beneath eye level. Do not tilt your head up or down or left and right. Ensure that your head is facing directly towards the light
Ensure that the subject is sitting/standing in the centre of the frame. Leave a space between the top of the head and the top of the frame. Do not stand to the left or right of the frame.
After pressing record pause for a 5 seconds to compose yourself before starting. This will ensure that there is no missed words at the start of the video. Repeat this at the end leaving the video for 3/4 seconds before pressing stop
Avoid recording in any video in rooms that have loud consistent noise. Turn off fans or TV before recording to ensure audio is captured cleanly.
Be sure to practice before you start. If you are unhappy with a video do it again.
TO SUM UP
Its all trail and error with these things but the important part is to start and continue to improve. Most people will hate the 1st, 2nd, 3rd and even 4th video you do. If you are me you will probably dislike all the things you do. But follow the steps above and learn from your mistakes and you will be acing your video's in no time