How to make thumbnail for YouTube video

YouTube provides 3 images from your video as the thumbnail. You can either select one from them or upload your own thumbnail within 2MB. Custom thumbnail generally attracts more views hence their use is a must.
Rule of thumb for designing thumbnail is never even click-bait. As mentioned in this article click bait is useful for short time but not for long time. Use following suggestions to improve on thumbnail design.

• Use a simple background but not pure white.
• Use colors which are easily recognizable.
• Add small text in thumbnail.
• add the 1-2 contents of video (e.g. ball, apple) in thumbnail.
• Use proper width-height ratio (e.g. 720x1080)

You can use photoshop/paint or any other software (whichever suits you).

Thumbnails always have more potential to get clicked than simple links.