I can say that drawing tears is one of the simplest techniques in drawing. Seriously, for starters, try to draw eyes, draw eyebrows, and then just try to draw drops of water that flow from the eyes. Well, or you can just read some article about it, there are quite a lot of them. For example, here
https://wowpencils.com/how-to-draw-tears/ it is shown in some detail how to draw tears. Also try to sketch from someone else's work, this can help you with practice. Good luck